Jazz band instrument (7)
(Other definitions for trumpet that I've seen before include "beastly noise" , "Play it" , "Army instrument for signals" , "What elephants do" , "Orchestral or military instrument" .)
'jazz band instrument' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sax that I've seen before include "Music-maker" , "Wind instrument (abbr)" , "Jazz instrument (abbr)" .)