Perhaps cold egg in Irish stew (8)
I believe the answer is:
rhinitis
'perhaps cold' is the definition.
The definition suggests a singular noun which matches the answer.
'egg in irish stew' is the wordplay.
'egg' becomes 'nit' (a nit is an insect egg).
'in' indicates putting letters inside.
'stew' is an anagram indicator.
'irish' anagrammed gives 'rhiis'.
'nit' put into 'rhiis' is 'RHINITIS'.
Can you help me to learn more?
(Other definitions for rhinitis that I've seen before include "Nasal inflammation" , "nasal affliction" , "Inflammation of the lining of the nose" , "trouble with the beak" , "Medical complaint" .)