Stronghold of chess? (6)
I believe the answer is:
castle
This clue might be a double definition.
'stronghold' is the first definition.
(I know that castle is a type of citadel)
'chess?' is the second definition.
The definition and answer can be both acts as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'of' acts as a link.
Can you help me to learn more?
(Other definitions for castle that I've seen before include "Chateau" , "eg Edinburgh or Windsor" , "Rook, on chess board" , "Move two pieces" , "Man on board" .)