4 down
US
lawman
perfects
hearing
aid
(9)
US lawman perfects hearing aid (9)
hints
0
checks
0
hints
The definition is at the end of the clue.
How the clue works
Look at hearing aid — that's your definition. You've got EARP, the famous US lawman Wyatt Earp, followed by HONES meaning perfects (as in sharpens), and stick those together and you're there.