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