Willing to support objective when mate approaches? (7)
I believe the answer is:
endgame
'when mate approaches?' is the definition.
(part of a chess game leading to checkmate)
'willing to support objective' is the wordplay.
'willing' becomes 'game' (game can mean willing to do something).
'to support' says to put letters next to each other (in a down clue, some letters hold up others).
'objective' becomes 'end' (both can mean a purpose).
'game' put after 'end' is 'ENDGAME'.
(Other definitions for endgame that I've seen before include "Final stage in a contest" , "contest's final stage" , "close to board meeting" , "Beckett play" , "final moves" .)