Bang shut (4)
I believe the answer is:
'bang shut' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for slam that I've seen before include "(Almost) all the tricks" , "Shut hard" , "Shut (a door) noisily" , "Criticise - attack" , "Severely criticise; shut (a door) forcefully" .)