Hearing a noise is irritating (6)
I believe the answer is:
annoys
'noise is irritating' is the definition.
I can't tell whether this definition defines the answer.
'hearing a' is the wordplay.
I cannot really see how this works, but
'a' could be 'an' and 'an' is found within the answer.
The remaining letters 'noys' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for annoys that I've seen before include "Nettles" , "Irks, vexes" , "Bugs" , "Causes irritation" , "Irritates, vexes" .)