Grounds for affair? (8)
I believe the answer is:
occasion
I believe this clue is a double definition.
'grounds' is the first definition.
(thesaurus)
'affair?' is the second definition.
('occasion' can be a synonym of 'affair')
'for' acts as a link.
(Other definitions for occasion that I've seen before include "Time of a particular event" , "Special event or celebration" , "A special event, or the time it happens" , "Opportunity" , "Cocoa's in (anag.)" .)