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 the answer is hidden within the clue.
'RAT' can be found hidden inside 'crate'.
(Other definitions for rat that I've seen before include "Abandon" , "shopper" , "Sewer rodent" , "Unpleasant character" , "Inform" .)