Criticise them, viciously, though tennis star's grand? (4)

I believe the answer is:

slam

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'criticise' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

(Other definitions for slam that I've seen before include "Violently strike against" , "Ambitious contract" , "Shut (a door) noisily" , "Shut violently" , "Criticise - bang - very good result at bridge" .)

I've seen this clue in The Irish Times.

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