Maintain feature of castle (4)
I believe the answer is:
keep
This could be a double definition.
'maintain feature' is the first definition.
'keep' can be an answer for 'maintain' ('keep' can be a synonym of 'maintain'). I am not sure about the 'feature' bit.
'castle' is the second definition.
(thesaurus)
'of' acts as a link.
Can you help me to learn more?
(Other definitions for keep that I've seen before include "Only one cricketer on field will" , "run" , "Dungeon" , "Remain" , "strong position" .)