Principal unenthusiastic? Coryza? (4,4)

I believe the answer is:

head cold

I'm a little stuck... Click here to teach me more about this clue!

'principal unenthusiastic? coryza?' is the definition.
The definition suggests a singular noun which matches the answer.

'principal unenthusiastic? coryza?' is the wordplay.
'principal' becomes 'head' (synonyms).
'unenthusiastic? coryza?' becomes 'cold' (I've seen this in another clue. I am not sure about the 'unenthusiastic?' bit.).
'head'+'cold'='HEAD COLD'

Can you help me to learn more?

(Other definitions for head cold that I've seen before include "Ailment blocking the nasal passages" , "complaint" , "What might block up nose and eyes" , "Common infection of the sinuses" .)

I've seen this clue in the Sydney Morning Herald.

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