Stronghold surrounding ancient city is beneficial (3,3,4)
I believe the answer is:
for the best
'stronghold surrounding ancient' is the definition.
I don't know anything about this answer so I cannot tell whether this works.
'city is beneficial' is the wordplay.
I cannot really understand how this works, but
'city' could be 'thebes' (Thebes is an example) and 'thebes' is found within the answer.
'beneficial' could be 'for' (I've seen this in other clues) and 'for' is found in the answer.
A single letter 't' remains which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for for the best that I've seen before include "With good intentions" , "with good reason" , "advantageous in the long term" .)