Duck kept in freezer overnight (4)
I believe the answer is:
zero
'duck' is the definition.
(I've seen this before)
'in freezer overnight' is the wordplay.
'in' says the answer is hidden in the clue.
'ZERO' is hidden within 'freezer overnight'.
'kept' acts as a link.
(Other definitions for zero that I've seen before include "Cipher for nothing" , "Japanese fighter" , "[NIX]" , "ending as nothing too" , "terribly cold" .)