Don't allow supporters in camp (8)
I believe the answer is:
barracks
'camp' is the definition.
(I've seen this before)
'don't allow supporters' is the wordplay.
'don't allow' becomes 'bar'.
'supporters' becomes 'racks' (I can't explain this - if you can you should give a lot more credence to this answer).
'bar'+'racks'='BARRACKS'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for barracks that I've seen before include "Buildings to accommodate armies" , "Military quarters" , "For the rest of the men" , "Buildings for soldiers" , "Building for military personnel" .)