Tease US composer for organ case (7)
I believe the answer is:
ribcage
'organ case' is the definition.
(I've seen this before)
'tease us composer' is the wordplay.
'tease' becomes 'rib' (rib can mean to tease or mock).
'us composer' becomes 'cage' (I've seen this in another clue).
'rib'+'cage'='RIBCAGE'
'for' acts as a link.
(Other definitions for ribcage that I've seen before include "Bones attached to the sternum" , "organ case" , "protects one's heart" , "Frame round the chest" , "bony frame" .)