Rodent inside crate (3)
I believe the answer is:
rat
'rodent' is the definition.
(rat is a kind of rodent)
'inside crate' is the wordplay.
'inside' indicates a hidden word.
'RAT' can be found hidden inside 'crate'.
(Other definitions for rat that I've seen before include "Abandon" , "shopper" , "Sewer rodent" , "Unpleasant character" , "Inform" .)