Wrong applications of such cavities (7)
I believe the answer is:
sinuses
'such cavities' is the definition.
'sinuses' can be an answer for 'cavities' (sinus is a kind of cavity). I am not sure about the 'such' bit.
'wrong applications' is the wordplay.
'wrong' becomes 'sin' (I've seen this before).
'applications' becomes 'uses' (I've seen this before).
'sin'+'uses'='SINUSES'
'of' is the link.
Can you help me to learn more?
(Other definitions for sinuses that I've seen before include "Top spaces" , "holes in the head" , "Cavities in skull connecting with nostrils" , "Empty spaces" .)