Make effort to surround old city (4)
I believe the answer is:
troy
'city' is the definition.
(Troy is an example)
'make effort to surround old' is the wordplay.
I cannot quite understand how this works, but
'old' could be 'o' (common abbreviation eg in OE for Old English) and 'o' is found in the answer.
'effort' could be 'try' (synonyms) and 'try' is present in the leftover letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for troy that I've seen before include "Legendary ancient city of northwest Anatolia" , "Hardy sergeant" , "Priam's city" , "Ancient city in Asia Minor" , "Precious stone weight system" .)