Recital isn't ruined with tense musician (12)
I believe the answer is:
clarinettist
'musician' is the definition.
(I know that clarinettist is a type of musician)
'recital isn't ruined with tense' is the wordplay.
'ruined with' indicates an anagram.
'tense' becomes 't' (grammatical abbreviation).
'recital'+'isnt'='recitalisnt'
'recitalisnt' anagrammed with 't' makes 'CLARINETTIST'.
(Other definitions for clarinettist that I've seen before include "Musician, like Benny Goodman, say" , "Cats in litter (anag) -- woodwind player" .)