Party leader, the French, a positive delight (8)
I believe the answer is:
pleasure
'delight' is the definition.
('pleasure' can be a synonym of 'delight')
'party leader the french a positive' is the wordplay.
'party leader' becomes 'p' (I've seen this in other clues).
'the french' becomes 'le'.
'positive' becomes 'sure' ('sure' can be similar in meaning to 'positive').
'p'+'le'+'a'+'sure'='PLEASURE'
(Other definitions for pleasure that I've seen before include "diversion" , "A repulse (anag.)" , "Enjoyment, happiness" , "contentment" , "Feeling of enjoyment or satisfaction" .)