Left one capital to go round another (6)
I believe the answer is:
berlin
'left one capital to go round another' is the definition.
I can't judge whether this defines the answer.
'left one capital to go round' is the wordplay.
'left' becomes 'l' (common abbreviation).
'one' becomes 'i' (Roman numeral).
'capital' becomes 'bern' (capital of Switzerland).
'to go round' is an insertion indicator.
'l'+'i'='li'
'li' going inside 'bern' is 'BERLIN'.
Can you help me to learn more?
(Other definitions for berlin that I've seen before include "2 [PHILOSOPHER]" , "capital city" , "German city" , "Composer of White Christmas" , "A once-divided city" .)