Put your foot down, Frank (5)
I believe the answer is:
stamp
I believe this is a double definition.
'put your foot down' is the first definition.
(stamp your feet)
'frank' is the second definition.
(frank can mean to mark with an official stamp)
(Other definitions for stamp that I've seen before include "Impress; postage sticker" , "Official mark; bang (foot)" , "Mark of approval" , "put one's foot down hard" , "Evidence of payment of postage duty" .)