On the phone, mention also experiencing irritation of the glands (7)
I believe the answer is:
adenoid
'on' is the definition.
Although both the answer and definition are adjectives, I cannot see how they can define each other.
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for adenoid that I've seen before include "Gland-like - I add one (anag)" , "Glandular" .)