Stay within a stronghold (4)
I believe the answer is:
keep
This clue could be a double definition.
'stay within' is the first definition.
'keep' can be an answer for 'stay' (keeping is a kind of staying). I'm unsure of the 'within' bit.
'a stronghold' is the second definition.
(keep is a kind of stronghold)
Can you help me to learn more?
(Other definitions for keep that I've seen before include "Retain in old castle tower?" , "strong position" , "Stock" , "Retain; strong tower" , "Subsistence" .)