Attempt to surround old city (4)
I believe the answer is:
troy
'city' is the definition.
(Troy is an example)
'attempt to surround old' is the wordplay.
'attempt' becomes 'try' (I've seen this before).
'to surround' means one lot of letters goes inside another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'try' going around 'o' is 'TROY'.
(Other definitions for troy that I've seen before include "City besieged by Greeks to rescue Helen" , "Helen of --, beauty" , "City besieged by the Greeks - system of gem weight measurement" , "part of Asia Minor" , "Hardy sergeant" .)