Major dis (4)
I believe the answer is:
slam
'major dis' 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 "Shut (a door) noisily" , "A grand one is 13 tricks" , "Winning all (or all but one) of the tricks in bridge" , "Close noisily" , "(Almost) all the tricks" .)