Stressful hearing (6)
I believe the answer is:
trying
I believe this is a double definition.
'stressful' is the first definition.
('trying' can be a synonym of 'stressful')
'hearing' is the second definition.
('try' can be a synonym of 'hear')
(Other definitions for trying that I've seen before include "Making attempts" , "Attempting or stretching patience to the limit" , "Troublesome - but making an effort" , "Upsetting" , "Testing" .)