Roast starter of smoked meat cut (4)
I believe the answer is:
'roast' is the definition.
(I've seen this in another clue)
'starter of smoked meat cut' is the wordplay.
'starter of' indicates taking the first letters.
'meat' becomes 'lamb' (lamb is a kind of meat).
'cut' means to remove the last letter.
The initial letter of 'smoked' is 's'.
'lamb' with its final letter taken off is 'lam'.
(Other definitions for slam that I've seen before include "Winning of 12 or 13 tricks at bridge" , "what needs a lot of tricks to succeed" , "Shut violently" , "Report of forcefully closing" , "ambitious bid" .)