Improvised recital includes new instrument (8)
I believe the answer is:
clarinet
'instrument' is the definition.
(clarinet is a kind of instrument)
'improvised recital includes new' is the wordplay.
'improvised' indicates an anagram (letters are improvised or randomised).
'includes' is an insertion indicator.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'recital' anagrammed gives 'clariet'.
'clariet' enclosing 'n' is 'CLARINET'.
(Other definitions for clarinet that I've seen before include "Woodwind instrument played by Artie Shaw and Benny Goodman" , "member of orchestra" , "musician" , "Source of music" , "Wind instrument made from Clare tin" .)