Everything in pallet (3)
I believe the answer is:
all
'everything' is the definition.
(I've seen this before)
'in pallet' is the wordplay.
'in' says the answer is hidden in the clue.
'ALL' is hidden within 'pallet'.
(Other definitions for all that I've seen before include "Every single one" , "The whole amount" , "Wholly" , "Monopolist controls this" , "None excluded" .)