Look shown by mature aristocrats? (7)
I believe the answer is:
peerage
'aristocrats?' is the definition.
(members of the peerage)
'look shown by mature' is the wordplay.
'look' becomes 'peer' (to peer at something is to look at it).
'shown by' is a charade indicator (letters next to each other).
'mature' becomes 'age' (synonyms).
'peer'+'age'='PEERAGE'
(Other definitions for peerage that I've seen before include "Aristocracy" , "The nobility en masse" , "Book of the nobility" , "Ranks of the nobility" , "Noble title and rank" .)