Play guitar with favourite loose woman (8)
I believe the answer is:
strumpet
'loose woman' is the definition.
('strumpet' can be a synonym of 'loose woman')
'play guitar with favourite' is the wordplay.
'play guitar' becomes 'strum' (I've seen this before).
'with' is a charade indicator (letters next to each other).
'favourite' becomes 'pet' ('pet' can be a synonym of 'favourite').
'strum'+'pet'='STRUMPET'
(Other definitions for strumpet that I've seen before include "Whore" , "Tart" , "Harlot" , "Hussy" , "Trumpets for loose woman" .)