Relative was sorry about nobility (8)
I believe the answer is:
grandeur
'nobility' is the definition.
(I know that nobility can be written as grandeur)
'relative was sorry about' is the wordplay.
'relative' becomes 'gran' (short for grandmother).
'was sorry' becomes 'rued ' (to rue something is to regret it).
'about' shows that the letters should be reversed in order.
'rued' back-to-front is 'deur'.
'gran'+'deur'='GRANDEUR'
(Other definitions for grandeur that I've seen before include "state" , "Impressiveness of appearance" , "Nobility, dignity" , "Splendour or magnificence" , "Splendour, impressiveness" .)