Unusual article about new musical instrument (8)
I believe the answer is:
clarinet
'musical instrument' is the definition.
(I know that Clarinet is a type of transposing instrument)
'unusual article about new' is the wordplay.
'unusual' is an anagram indicator.
'about' means one lot of letters goes inside another.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'article' with letters rearranged gives 'clariet'.
'clariet' going around 'n' is 'CLARINET'.
(Other definitions for clarinet that I've seen before include "Woodwind instrument - Artie Shaw played one" , "Wind instrument made from Clare tin" , "Single reed woodwind instrument" , "Source of music" , "Woodwind instrument played by Artie Shaw and Benny Goodman" .)