Noble from circle in a London borough? (7)
I believe the answer is:
baronet
'noble' is the definition.
(I know that baronet is a type of baron)
'circle in a london borough?' is the wordplay.
'circle' becomes 'O' (O is a circle).
'in' means one lot of letters goes inside another.
'a london borough?' becomes 'Barnet' (Barnet is a borough of London).
'o' inserted within 'barnet' is 'BARONET'.
'from' is the link.
(Other definitions for baronet that I've seen before include "A Breton could be a British peer" , "Lowest British hereditary title" , "Lowest hereditary title of honour" , "Aristocrat" , "Minor noble" .)