Estate supporting smart youth leader (8)
I believe the answer is:
property
'estate' is the definition.
(I've seen this before)
'supporting smart youth leader' is the wordplay.
'supporting' becomes 'pro' (being pro something is supporting it).
'smart' becomes 'pert' (I've seen this in another clue).
'youth leader' becomes 'y' (I've seen this in other clues).
'pro'+'pert'+'y'='PROPERTY'
(Other definitions for property that I've seen before include "(A) characteristic; land, stocks etc." , "Attribute; chattel" , "Tangible possession" , "Something owned" , "Possessions; characteristic" .)