To look one's years requires nobility (7)
I believe the answer is:
peerage
'nobility' is the definition.
(I know that peerage is a type of nobility)
'to look one's years' is the wordplay.
'to look' becomes 'peer' (peering is a kind of looking).
'one's years' becomes 'age'.
'peer'+'age'='PEERAGE'
'requires' acts as a link.
(Other definitions for peerage that I've seen before include "Group of lords" , "Book of the nobility" , "Lordly group" , "Book listing nobles" , "Dukes, earls, lords, ladies - the lot" .)