Loud sound hurt ears, initially shocking (10)
I believe the answer is:
thunderous
'loud' is the definition.
(similar in meaning)
'sound hurt ears initially shocking' is the wordplay.
'initially' says to take the initial letters.
'shocking' indicates anagramming the letters (letters shocked or shaken).
The first letter of 'ears' is 'e'.
'sound'+'hurt'+'e'='soundhurte'
'soundhurte' with letters rearranged gives 'THUNDEROUS'.
(Other definitions for thunderous that I've seen before include "Loud and rumbling" , "Deafening" .)