Clandestine romance just beyond a female (6)
I believe the answer is:
affair
'clandestine romance' is the definition.
(I've seen this before)
'just beyond a female' is the wordplay.
'just' becomes 'fair' ('fair' is associated in meaning with 'just').
'beyond' is a charade indicator (letters next to each other).
'a female' becomes 'af' (I've seen this in other clues).
'fair' after 'af' is 'AFFAIR'.
(Other definitions for affair that I've seen before include "A matter; amorous episode" , "Extramarital activity" , "A matter, perhaps of love" , "Romantic relationship between two unmarried people" , "Concern, matter, business" .)