Let party leader go in delight (5)
I believe the answer is:
lease
'let' is the definition.
(as in to lease or let a building)
'party leader go in delight' is the wordplay.
'party' becomes 'l'.
'leader' becomes 'e' (I've seen this in other clues).
'go in delight' becomes 'ase' (I can't justify this - if you can you should give a lot more credence to this answer).
'l'+'e'+'ase'='LEASE'
Can you help me to learn more?
(Other definitions for lease that I've seen before include "Tenancy contract" , "Let; rent" , "Let for money" , "Rent (a property)" , "Rent -- easel (anag)" .)