Revolutionary determined to keep bishop in stronghold (7)
I believe the answer is:
redoubt
'stronghold' is the definition.
(I know that redoubt is a type of stronghold)
'revolutionary determined to keep bishop' is the wordplay.
'revolutionary' becomes 'red' (red can informally mean communist).
'determined' becomes 'out'.
'to keep' means one lot of letters goes inside another.
'bishop' becomes 'B' (chess abbreviation).
'out' placed around 'b' is 'oubt'.
'red'+'oubt'='REDOUBT'
'in' is the link.
(Other definitions for redoubt that I've seen before include "Fieldwork defending a pass" , "21 ac fortification" , "Defensive outwork" , "Military defence-work" , "Temporary or outward fortification" .)