Tear down line in protest before I shut up (8)
I believe the answer is:
demolish
'tear down' is the definition.
(I've seen this before)
'line in protest before i shut up' is the wordplay.
'line' becomes 'l'.
'in' indicates putting letters inside.
'protest' becomes 'demo' (I've seen this before).
'before' says to put letters next to each other.
'shut up' becomes 'sh'.
'demo'+'i'='demoi'
'l' put inside 'demoi' is 'demoli'.
'demoli'+'sh'='DEMOLISH'
(Other definitions for demolish that I've seen before include "Knock down, say a building" , "Raze to the ground" , "Knock or tear down" , "Break down" , "Pull or tear down" .)