Plain individual, but partial (8)
I believe the answer is:
overtone
'partial' is the definition.
(thesaurus)
'plain individual' is the wordplay.
'plain' becomes 'overt' (I've seen this in another clue).
'individual' becomes 'one' (an individual is one person).
'overt'+'one'='OVERTONE'
'but' acts as a link.
(Other definitions for overtone that I've seen before include "Subtle extra meaning" , "Innuendo perhaps" , "Subtle implication or connotation" , "Hint" , "part of harmonic series" .)