Vitriolic boxer takes in new specialist (7)
I believe the answer is:
pungent
'vitriolic' is the definition.
(thesaurus)
'boxer takes in new specialist' is the wordplay.
'boxer' becomes 'pug' (short for pugilist - term for boxer).
'takes in' means one lot of letters goes inside another.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'specialist' becomes 'ent' (Ear, Nose and Throat specialist).
'pug' going around 'n' is 'pung'.
'pung'+'ent'='PUNGENT'
(Other definitions for pungent that I've seen before include "Acrid - painful" , "Penetrating" , "Offensive" , "Sharply tasting or smelling" , "Sharp tasting/smelling" .)