Keeps the rooks (7)
I believe the answer is:
castles
I believe this is a double definition.
'keeps' is the first definition.
(I've seen this before)
'the rooks' is the second definition.
('castle' can be a synonym of 'rook')
(Other definitions for castles that I've seen before include "Men" , "Forts" , "English homes?" , "big houses" , "Fortresses" .)