Butterfly's relative (4)
I believe the answer is:
moth
'butterfly's relative' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for moth that I've seen before include "Usually nocturnal insect" , "Insect; MND fairy" , "night flyer" , "one drawn to the bright lights" , "Insect of the order lepidoptera" .)