Strike at revolutionary -- brave man in military unit (9)
I believe the answer is:
battalion
'military unit' is the definition.
(I know that battalion is a type of army unit)
'strike at revolutionary brave man' is the wordplay.
'strike' becomes 'bat'.
'revolutionary' shows that the letters should be reversed in order.
'brave man' becomes 'lion' ().
'at' in reverse letter order is 'ta'.
'bat'+'ta'+'lion'='BATTALION'
'in' is the link.
(Other definitions for battalion that I've seen before include "group of companies" , "Army unit" , "Military unit" , "Large body of troops" , "Army formation" .)