Instrument of terror deployed to limit parliamentary bill (9)
I believe the answer is:
retractor
'instrument' is the definition.
(retractor is a kind of instrument)
'terror deployed to limit parliamentary bill' is the wordplay.
'deployed' indicates an anagram.
'to limit' means one lot of letters goes inside another.
'parliamentary bill' becomes 'act'.
'terror' with letters rearranged gives 'retror'.
'retror' placed around 'act' is 'RETRACTOR'.
'of' acts as a link.
(Other definitions for retractor that I've seen before include "One withdraws" , "Instrument" , "Muscle" , "It must pull back" , "that springs back in reverse?" .)