Inside solitary fellow there's a capital chap (8)
I believe the answer is:
londoner
'a capital chap' is the definition.
(chap living in a capital city)
'inside solitary fellow' is the wordplay.
'inside' means one lot of letters goes inside another.
'solitary' becomes 'loner' (I've seen this in another clue).
'fellow' becomes 'don' (both can mean an academic).
'loner' placed around 'don' is 'LONDONER'.
'there's' is the link.
(Other definitions for londoner that I've seen before include "Native of Camberwell, perhaps" , "capitalist?" , "Native of Notting Hill or Camden, say" , "Inhabitant of capital" , "British citizen" .)