One who forbids the use of flag? (6)
I believe the answer is:
banner
I believe this is a double definition.
'one who forbids the use of' is the first definition.
(someone who bans things)
'flag?' is the second definition.
(I know that banner is a type of flag)
(Other definitions for banner that I've seen before include "Especially good" , "Standard carried at demo etc" , "Long flag" , "Flag; headline" , "Streamer for advertising" .)