Flirt with many a friend (5)
I believe the answer is:
dally
'flirt' is the definition.
('dally' can be a synonym of 'flirt')
'with many a friend' is the wordplay.
'with' is a charade indicator (letters next to each other).
'many' becomes 'd'.
'a friend' becomes 'ally' ('ally' can be a synonym of 'friend').
'd' next to 'ally' is 'DALLY'.
(Other definitions for dally that I've seen before include "Waste time" , "Move slowly" , "Procrastinate" , "Trifle" , "Dawdle - delay" .)