Pet butterfly? (6)
I believe the answer is:
stroke
I believe this clue is a double definition.
'pet' is the first definition.
(I've seen this before)
'butterfly?' is the second definition.
(butterfly stroke is a swimming stroke)
(Other definitions for stroke that I've seen before include "Blow - gentle touch - brain damage" , "Manner of swimming - caress with hand" , "Brain haemorrhage or caress" , "Medical seizure - effect of sun - oarsman" , "A blow or brain seizure" .)