Smash slate (4)
I believe the answer is:
slam
I believe this clue is a double definition.
'smash' is the first definition.
(thesaurus)
'slate' is the second definition.
(thesaurus)
(Other definitions for slam that I've seen before include "Shut violently" , "Shut loudly and forcibly" , "Winning of 12 or 13 tricks at bridge" , "Close noisily" , "major contract" .)