Large wind instrument (7)
(Other definitions for organ that I've seen before include "with a lofty tone?" , "Medium; body part" , "With prompt enthusiasm" , "Possibly stomach" , "Air-powered instrument" .)
(Other definitions for bassoon that I've seen before include "Instrument heard by Wedding-Guest" , "No, a boss would be a musical instrument" , "Hollow instrument" , "Tenor of the oboe family" , "Instrument - no ASBOs (anag)" .)