A professional has a place in this scheme (11)
I believe the answer is:
proposition
'this scheme' is the definition.
(I've seen this before)
'a professional has a place' is the wordplay.
'a professional' becomes 'pro' (abbreviation).
'has' says to put letters next to each other.
'a place' becomes 'position' (synonyms).
'pro'+'position'='PROPOSITION'
'in' is the link.
(Other definitions for proposition that I've seen before include "Offer" , "Suggested plan" , "Premise - suggestion" , "to try to get off with" , "selection" .)