Close with a bang (4)
I believe the answer is:
slam
'close with a bang' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for slam that I've seen before include "Criticise - bang - very good result at bridge" , "Taking of twelve or thirteen tricks (bridge)" , "Ambitious contract" , "big contract" , "Report of forcefully closing" .)