Monotonous droning noise reaches the hearer (7)
I believe the answer is:
humdrum
'monotonous' is the definition.
(I know that monotonous can be written as humdrum)
'noise reaches the hearer' is the wordplay.
'noise' becomes 'hum' (humming is a kind of noising).
'reaches the hearer' becomes 'drum' (I am not sure about this - if you are sure you should believe this answer much more).
'hum'+'drum'='HUMDRUM'
'droning' acts as a link.
This may not be right. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for humdrum that I've seen before include "Dull, monotonous" , "Unexciting" , "without incident" , "Dull and uninteresting" , "Boringly monotonous" .)