Rash old city teacher primarily in charge of some music? (9)
I believe the answer is:
urticaria
'rash' is the definition.
(urticaria is a kind of rash)
'old city teacher primarily in charge of some music?' is the wordplay.
'old city' becomes 'ur' (ancient city state).
'primarily' indicates taking the first letters.
'in charge of' becomes 'ic'.
'some music?' becomes 'aria' (aria is a kind of music).
The initial letter of 'teacher' is 't'.
'ur'+'t'+'ic'+'aria'='URTICARIA'
(Other definitions for urticaria that I've seen before include "Nettlerash" , "hives" , "complaint" , "Nettle rash" .)