Nag sounded grating (6)
I believe the answer is:
hoarse
'grating' is the definition.
(thesaurus)
'nag sounded' is the wordplay.
'nag' becomes 'horse' (I've seen this before).
'sounded' indicates a 'sounds like' (homophone) clue.
'horse' sounds like 'HOARSE'.
(Other definitions for hoarse that I've seen before include "(Of voice) rough, harsh" , "Of voice, rasping or gruff" , "With a rough husky voiced" , "With strained voice" , "Raucous" .)