Cut wood supporting seats (4,5)
I believe the answer is:
Here is my best explanation:
'cut' is the definition.
(rump steak is a kind of cut)
'wood supporting seats' is the wordplay.
'wood' becomes 'teak' (teak is a kind of wood).
'supporting' says to put letters next to each other (in a down clue, some letters go below others).
'seats' becomes 'rumps' ('rump' can be a synonym of 'seat').
'teak' after 'rumps' is 'RUMP STEAK'.