You wouldn't be able to use pluck
on the query but you can use select
if you want to limit the fields returned with eager loading.
You just need to make sure you include the id
so that Eloquent can match the relationships correctly e.g.:
$something = Something::with(array('something_else' => function($query){
$query->select('id', 'field');
}))->first();
With Laravel >= 5.5, you can specify the columns you want included by appending :
followed by a comma separated list of the fields. This means the above can be simplified to:
$something = Something::with('something_else:id,field')->first();
Please note that the related column fields need to be included for this to work i.e. the id
for "belongs" relationships or *_id
for "has" relationships (and *_type
if polymorphic).