Restrain that woman blocking a politician (6)
I believe the answer is:
hamper
'restrain' is the definition.
(hampering is a kind of restraining)
'woman blocking a politician' is the wordplay.
'woman' becomes 'her' (her refers to a woman).
'blocking' means one lot of letters goes inside another (to block can mean to block in or contain).
'politician' becomes 'mp' (Member of Parliament).
'a'+'mp'='amp'
'her' placed around 'amp' is 'HAMPER'.
'that' acts as a link.
(Other definitions for hamper that I've seen before include "basket case?" , "Picnic box" , "Food-basket" , "cramp" , "Food parcel" .)