Why is the frame only showing the last button? I'm using Tkinter for this

Question

I tried making this to have 2 buttons and a prompt, with the buttons being side by side on a grid. However, I notice that when I run the program only the last button is shown, with a blank screen and the button "Add Terms". I'm not sure why this is happening, my idea is that for some reason the self.clearFrame() is running even though it's a command parameter. Thanks

        self.root = tk.Tk()
        self.root.geometry("500x500")
        self.root.title("VocabMaster")
    
        self.prompt = tk.Label(self.root, text = "What would you like to do?", font = ('Arial', 18))
        self.prompt.pack(padx = 10, pady = 10)

        self.frame = tk.Frame(self.root)
        practiceButton = tk.Button(self.frame, text = f"Practice {len(self.currentReviewList)} terms", font = ('Arial, 20'), command=self.startPractice())
        practiceButton.grid(row = 0, column=0)

        addItems = tk.Button(self.frame, text = "Add Items", font = ('Arial', 20), command= self.addItem())
        addItems.grid(row= 0, column= 1)
        
        self.frame.pack()
        self.root.mainloop()


    def clearFrame(self):
        self.prompt.destroy()
        for widgets in self.frame.winfo_children():
            widgets.destroy()
        
    def startPractice(self):
        self.clearFrame()

        for item in self.currentReviewList:
            prompt = tk.Label(self.root, text = f"Definition of {item.item_name}?")
            prompt.pack()
            answerBox = tk.Entry(self.root).place(x = 250, y = 100)
            answerBox.pack()
            
            answer = answerBox.get()
            # Gets the correct answer
            # need to move it to next level, display correct, and update it's time.
            if answer == item.item_definition:
                # Displaying correct
                correct = tk.Button(self.root, text = "Correct!", font = ('Arial', 10))
                # Fixing level
                item.item_level+=1
                # Updating time for next review
                item = HelperMethods.getNewHoursForItem(item)
                correct.pack()
            # Gets the wrong answer
            else:
                # demoting level
                item.item_level-=1

                # Updating time for next reviwe
                item = HelperMethods.getNewHoursForItem(item)

                #Displaying definition, as well as informing of incorrect
                definitionLabel = tk.Label(self.root, text = f"Wrong! Correct definition is {item.item_definition}")
                definitionLabel.pack()
                nextButton = tk.Button(self.root, text = "Next", font = ('Arial', 10))
                nextButton.pack()
            self.clearFrame()
    def addItem(self):
        self.clearFrame()        

        term_frame = tk.Frame(self.root)
        term_label = tk.Label(term_frame, text = "Please enter the term you would like to add", font = ('Arial', 16))
        term_label.grid(row = 0, column=0)
        t_entry = tk.Entry(term_frame)
        t_entry.grid(row = 0, column=0)

        defn_frame = tk.Frame(self.root)
        defn_label = tk.Label(defn_frame, text = "Please enter the definition of the term", font = ('Arial', 16))
        defn_label.grid
        d_entry = tk.Entry(defn_frame)
        d_entry.grid(row = 0, column=1)