"Charm ____ with air, and agony with words” (Much Ado About Nothing) (4)
I believe the answer is:
ache
'charm with air and agony with words much ado' is the definition.
I can't tell whether this definition defines the answer.
'about nothing' is the wordplay.
'about' becomes 'a' (abbreviation in Chambers).
'nothing' becomes 'che' (I am not sure about this - if you are sure you should believe this answer much more).
'a'+'che'='ACHE'
Can you help me to learn more?
(Other definitions for ache that I've seen before include "agony" , "Cause pain" , "anguish" , "Feel pain" , "Dull prolonged pain" .)