Cold in the head (7)
I believe the answer is:
catarrh
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">cold in the head</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(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" .)