Queen in flit with philanderer (5)
I believe the answer is:
Here is my best explanation:
'philanderer' is the definition.
'queen in flit' is the subsidiary indication.
'queen' becomes 'r' (r is abbreviation regina. e.g. in ER ).
'in' indicates putting letters inside.
'r' put inside 'flit' is 'flirt'.
'with' is the link.
(Other definitions for flirt that I've seen before include "Behave playfully with opposite sex", "Chat (someone) up", "Engage lightheartedly in amorous banter", "Dalliance", "Coquet", "Saucy girl", "Philander(er)", "Play at courtship", "Be playfully amorous" and "Behave amorously, without serious intentions".)