Cold in the head (7)
I believe the answer is:
catarrh
'cold in the head' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for catarrh that I've seen before include "Inflammation of membrane of nose and throat" , "Problem with cold" , "Nasal inflammation" , "Arch rat with inflamed mucous membrane" , "Inflammation often blocking the nose" .)