A little decoy puzzled rodent (5)
I believe the answer is:
coypu
'rodent' is the definition.
(I know that coypu is a type of rodent)
'a little decoy puzzled' is the wordplay.
'a little' indicates a hidden word (a little bit of the clue).
'COYPU' can be found hidden inside 'decoy puzzled'.
(Other definitions for coypu that I've seen before include "South American rodent bred for its fur, nutria" , "Beaver-like animal" , "rodents" , "Animal -- source of nutria fur" , "Aquatic beaver-like rodent" .)