City brute running wild – one to be caught (6)
I believe the answer is:
beirut
'city' is the definition.
(I know that Beirut is a national capital)
'brute running wild one to be caught' is the wordplay.
'running wild' is an anagram indicator.
'one' becomes 'i' (Roman numeral).
'to be caught' indicates putting letters inside.
'brute' with letters rearranged gives 'berut'.
'berut' placed around 'i' is 'BEIRUT'.
(Other definitions for beirut that I've seen before include "Middle East capital" , "Lebanon's capital" , "Capital of 21 across" , "Lebanese capital" , "Capital city of Lebanon" .)