Musician’s son’s boast I misconstrued (10)
I believe the answer is:
bassoonist
'musician's' is the definition.
(bassoonist is a kind of musician)
'son's boast i misconstrued' is the wordplay.
'misconstrued' is an anagram indicator.
'sons'+'boast'+'i'='sonsboasti'
'sonsboasti' anagrammed gives 'BASSOONIST'.
(Other definitions for bassoonist that I've seen before include "Musician" , "Woodwind player" .)