Hearing is difficult (6)
I believe the answer is:
trying
This clue is a double definition.
'hearing' is the first definition.
('try' can be a synonym of 'hear')
'difficult' is the second definition.
(similar in meaning)
'is' acts as a link.
(Other definitions for trying that I've seen before include "Difficult - annoying" , "Making an effort, or straining one's patience" , "Essaying" , "particularly awkward" , "job for a jury?" .)