Spiral ear cavity (7)
I believe the answer is:
cochlea
'spiral ear cavity' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for cochlea that I've seen before include "Coiled tube in the inner ear" , "Snail-shaped tube in the inner ear" , "A cloche (anag) - spiral cavity of the inner ear" , "Spiral tube in inner ear" , "there's a cavity, as we hear" .)