This sounds like a capital ramble (4)
I believe the answer is:
roam
'ramble' is the definition.
(I know that ramble can be written as roam)
'this sounds like a capital' is the wordplay.
'this sounds like' indicates a 'sounds like' (homophone) clue.
'a capital' becomes 'Rome' (capital of Italy).
'rome' is a homophone of 'ROAM'.
(Other definitions for roam that I've seen before include "Move about aimlessly" , "range" , "Prowl" , "wander around" , "Wander widely" .)