Sort of nonsense to silence! (4)
I believe the answer is:
tosh
'sort of nonsense' is the definition.
'to silence' is the wordplay.
'silence' becomes 'sh' (I've seen this in other clues).
'to'+'sh'='TOSH'
(Other definitions for tosh that I've seen before include "Boloney" , "Scottish chum" , "[BLAH]" , "Rubbish; shot (anagram)" , "Nonsense; shot (anag.)" .)