Exposed one French fellow radical (9)
I believe the answer is:
uncovered
'exposed' is the definition.
(I know that exposed can be written as uncovered)
'one french fellow radical' is the wordplay.
'one french' becomes 'un' ('one' in French).
'fellow' becomes 'cove' (British slang term).
'radical' becomes 'red' (red can mean a communist).
'un'+'cove'+'red'='UNCOVERED'
(Other definitions for uncovered that I've seen before include "Exposed, revealed" , "Crude oven (anag.)" .)