Booked - for a forthcoming wedding (7)
I believe the answer is:
engaged
This clue is a double definition.
'booked' is the first definition.
(synonyms)
'for a forthcoming wedding' is the second definition.
(as in being engaged to be married)
(Other definitions for engaged that I've seen before include "Spoken for" , "Employed - to be married? (7)" , "Busy; employed" , "Held" , "Fully committed - to get married?" .)