Prissy little chap, but original (6)
I believe the answer is:
primal
'original' is the definition.
('primal' can be a synonym of 'original')
'prissy little chap' is the wordplay.
'prissy' becomes 'prim' ('prim' can be a synonym of 'prissy').
'little' means to remove the last letter (the word is not quite complete).
'chap' becomes 'mal' (**).
'prim' with its final letter taken away is 'pri'.
'pri'+'mal'='PRIMAL'
'but' acts as a link.
(Other definitions for primal that I've seen before include "typifying some fear?" , "Primitive or fundamental" , "Of an early stage of development" , "Most important (scream therapy?)" , "Original or primitive" .)