Block silly vote (4)
I believe the answer is:
veto
'block' is the definition.
(I've seen this before)
'silly vote' is the wordplay.
'silly' indicates anagramming the letters.
'vote' with letters rearranged gives 'VETO'.
(Other definitions for veto that I've seen before include "Authoritative prohibition" , "Right to reject a decision" , "Right to reject a proposed measure" , "Throw out" , "Power to reject legislation" .)