Expert adding weight to yours truly in scheme (9)
I believe the answer is:
programme
'scheme' is the definition.
(thesaurus)
'expert adding weight to yours truly' is the wordplay.
'expert' becomes 'pro' (short for professional).
'adding' is a charade indicator (letters next to each other).
'weight' becomes 'gram' (unit of weight).
'to yours truly' becomes 'me' (the person who set this crossword).
'pro'+'gram'+'me'='PROGRAMME'
'in' acts as a link.
(Other definitions for programme that I've seen before include "Schedule of proceedings" , "Broadcast feature" , "Schedule of events" , "Menu of events" , "Curriculum" .)