Touchy about curtailed party — a mockery! (8)
I believe the answer is:
travesty
'a mockery' is the definition.
('travesty' can be a synonym of 'mockery')
'touchy about curtailed party' is the wordplay.
'touchy' becomes 'testy'.
'about' is an insertion indicator.
'curtailed' means to remove the last letter.
'party' becomes 'rave' (type of dance party).
'rave' with its last letter taken off is 'rav'.
'testy' placed around 'rav' is 'TRAVESTY'.
(Other definitions for travesty that I've seen before include "Take off" , "Mockery, grotesque imitation" , "Grotesque distortion" , "Vary test (anag.)" , "Charade" .)