Insects can be wickedly false (5)
I believe the answer is:
fleas
'insects' is the definition.
(flea is a kind of insect)
'wickedly false' is the wordplay.
'wickedly' indicates an anagram (I've seen this in other clues).
'false' anagrammed gives 'FLEAS'.
'can be' is the link.
(Other definitions for fleas that I've seen before include "Leaping parasites" , "Insects" , "jumpers" .)