Decongestant target (5)
I believe the answer is:
sinus
'decongestant target' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sinus that I've seen before include "Air-filled cavity in one's head" , "Cavity within a bone" , "Hollow space" , "Nasal cavity" , "Channel between brain and skull" .)