Castle tower (7)
(Other definitions for bastion that I've seen before include "Obtains in fortified place or stronghold" , "fortress" , "Obtains (anag.)" , "part of stronghold" , "Projecting part of a fortification" .)
'castle tower' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for turret that I've seen before include "Small corner tower" , "Little (e.g. castle) tower" , "Keep feature" , "Small tower on defensive wall - or tank" , "Small tower on building or tank" .)
'castle tower' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for keep that I've seen before include "Board and lodgings, perhaps" , "Retain or care for" , "Main tower of a medieval castle" , "Retain, maintain" , "Save" .)