Minor noble from circle in London borough (7)
I believe the answer is:
baronet
'minor noble' is the definition.
(I've seen this before)
'circle in london borough' is the wordplay.
'circle' becomes 'O' (O is a circle).
'in' means one lot of letters goes inside another.
'london borough' becomes 'Barnet' (Barnet is a borough of London).
'o' inserted into 'barnet' is 'BARONET'.
'from' is the link.
(Other definitions for baronet that I've seen before include "Tone bar (anag.)" , "Nobleman" , "Member of the British order of honour" , "One's entitled" , "Lower noble" .)