Gentleman keeled over, supporting girl coming out with rubbish (6)
I believe the answer is:
debris
'rubbish' is the definition.
(debris is a kind of rubbish)
'gentleman keeled over supporting girl coming out' is the wordplay.
'gentleman' becomes 'sir' (I've seen this before).
'keeled over' says the letters should be written backwards.
'supporting' means one lot of letters go next to another (in a down clue, some letters go below others).
'girl coming out' becomes 'deb' (short for debutante).
'sir' back-to-front is 'ris'.
'ris' put after 'deb' is 'DEBRIS'.
'with' is the link.
(Other definitions for debris that I've seen before include "Refuse, litter" , "Rebids for rubble" , "aftermath of wild reception?" , "Scattered remains" , "Rubble, heap of broken pieces" .)