Crossword Genius

Preserve part of a castle (4)

Ross

I believe the answer is:

keep

This clue is a double definition.

'preserve' is the first definition.
('keep' can be a synonym of 'preserve')

'part of a castle' is the second definition.
('keep' is part of 'castle')

(Other definitions for keep that I've seen before include "Act as custodian of" , "Board and lodging" , "Retain; strong tower" , "Continue" , "Guard" .)

I've seen this clue in the Evening Standard.
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