Model being married on boat (4)
I believe the answer is:
mark
'model' is the definition.
(thesaurus)
'married on boat' is the wordplay.
'married' becomes 'm' (abbreviation, e.g. in genealogy).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'boat' becomes 'ark' (ark is a kind of boat).
'm'+'ark'='MARK'
'being' is the link.
(Other definitions for mark that I've seen before include "Man's name; target" , "Scratch - German coin" , "follower of Jesus" , "Starting point in race" , "Scar; note" .)