Hearing difficult (6)
I believe the answer is:
trying
I believe this is a double definition.
'hearing' is the first definition.
('try' can be a synonym of 'hear')
'difficult' is the second definition.
(similar in meaning)
(Other definitions for trying that I've seen before include "Stressful" , "Troublesome - but making an effort" , "Vexatious - having a go" , "Causing strain, annoying" , "irksome" .)