Kind of leaf insect (4)
I believe the answer is:
flea
'insect' is the definition.
(flea is a kind of insect)
'kind of leaf' is the wordplay.
'kind of' is an anagram indicator.
'leaf' anagrammed gives 'FLEA'.
(Other definitions for flea that I've seen before include "Tiny parasite" , "source of infestation" , "Leaping insects" , "Jumping bloodsucker" , "Wingless, jumping insect" .)