Blow whistle in passage (8)
I believe the answer is:
windpipe
'passage' is the definition.
(I know that windpipe is a type of cartilaginous tube)
'blow whistle' is the wordplay.
'blow' becomes 'wind'.
'whistle' becomes 'pipe' (I've seen this before).
'wind'+'pipe'='WINDPIPE'
'in' acts as a link.
(Other definitions for windpipe that I've seen before include "Air passage to lungs, the trachea" , "The literal trachea" , "Common name for the trachea" , "The trachea, less formally" , "airline" .)