Flirt with husband into swinging (3,2)
I believe the answer is:
hit on
'flirt with' is the definition.
(I've seen this in another clue)
'husband into swinging' is the wordplay.
'husband' becomes 'h'.
'swinging' indicates anagramming the letters.
'into' is an anagram of 'iton'.
'h'+'iton'='HIT ON'
(Other definitions for hit on that I've seen before include "Try to get off with" , "Discover; single out" , "Discover, think of" , "Discovered suddenly or, in modern slang, made advances towards" , "Make advances to (US)" .)