Music producer is fashionable in red (8)
I believe the answer is:
clarinet
'music producer' is the definition.
'fashionable in red' is the wordplay.
'fashionable' becomes 'in' ('in' can be similar in meaning to 'fashionable').
'in' indicates putting letters inside.
'red' becomes 'claret' (claret is a kind of red**).
'in' put inside 'claret' is 'CLARINET'.
'is' is the link.
(Other definitions for clarinet that I've seen before include "Musical wind instrument as played by Benny Goodman" , "Woodwind instrument played by Artie Shaw and Benny Goodman" , "Find an instrument in claret" , "musician" , "Woodwind instrument - Artie Shaw played one" .)