A rally regularly held in old Asian city for capital street trader (6,4)
I believe the answer is:
pearly king
'capital street trader' is the definition.
The definition suggests a singular noun which matches the answer.
'a rally regularly held in old asian city' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'held in' means one lot of letters goes inside another.
'old asian city' becomes 'peaking' (I can't explain this - if you can you should believe this answer much more).
The alternate letters of 'rally' are 'rly'.
'rly' going within 'peaking' is 'PEARLY KING'.
'for' is the link.
Can you help me to learn more?
(Other definitions for pearly king that I've seen before include "Fancy London trader" , "Regal costermonger" , "Distinguished Londoner" .)