Marrying? Dump in future! (9)
I believe the answer is:
combining
'marrying?' is the definition.
The definition and answer can be both to do with social activities as well as being present participle verbs.
Maybe you can see an association between them that I can't see?
'dump in future' is the wordplay.
'dump' becomes 'bin' (I am not sure about this - if you are sure you should believe this answer much more).
'in' is an insertion indicator.
'future' becomes 'coming' ('coming' can be similar in meaning to 'future').
'bin' inserted inside 'coming' is 'COMBINING'.
Can you help me to learn more?
(Another definition for combining that I've seen is " Putting together to form a whole".)