Stroke and buff item of hardware (9,3)
I believe the answer is:
butterfly nut
'item of hardware' is the definition.
'stroke and buff' is the wordplay.
'stroke' becomes 'butterfly' (type of swimming stroke).
'and' means one lot of letters go next to another.
'buff' becomes 'nut' (both can mean an enthusiast or fan).
'butterfly'+'nut'='BUTTERFLY NUT'
(Other definitions for butterfly nut that I've seen before include "helping to make connections?" , "One screwed up" , "Two-winged fastener" , "Lepidopterist" .)