Could be aware, mystery man is causing trouble for The Hearing
I believe the answer is:
earwax
'causing trouble for the hearing' is the definition.
I can't tell whether this defines the answer.
'could be aware mystery man' is the wordplay.
'could be' indicates an anagram.
'mystery man' becomes 'x' (I am not sure about this - if you are sure you should believe this answer much more).
'aware' is an anagram of 'earwa'.
'earwa'+'x'='EARWAX'
'is' is the link.
Can you help me to learn more?
(Other definitions for earwax that I've seen before include "Soft yellow substance secreted by glands of a certain organ" , "Hearing problem" , "Secretion from aural glands" , "Secretion that can impair hearing" , "Soft yellow secretion - cerumen" .)