Pet butterfly, say (6)
I believe the answer is:
stroke
This clue is a double definition.
'pet' is the first definition.
(thesaurus)
'butterfly say' is the second definition.
(butterfly is a kind of stroke)
(Other definitions for stroke that I've seen before include "Rower's attack?" , "Caress; pencil mark" , "Apoplexy or blow as of whip" , "It's caused by interruption in blood-flow to the brain" , "Line made by pen" .)