Londoner, say, is an investor (10)
I believe the answer is:
capitalist
'investor' is the definition.
(I know that capitalist is a type of investor)
'londoner say is an' is the wordplay.
I cannot really see how this works, but
'is' is found in the answer.
'an' could be 'i' (Roman numeral for one) and 'i' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for capitalist that I've seen before include "rich man" , "Marx's bourgeois - a static lip (anag)" , "Profit-driven person" , "businessperson, maybe" , "investor" .)