Insect's adult stage (5)
I believe the answer is:
imago
'insect's adult stage' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for imago that I've seen before include "idealised figure" , "Last stage of insect's development" , "Final stage of insect development" , "Perhaps butterfly" , "imagines more than one" .)