Reliable racket (5)
I believe the answer is:
sound
This clue is a double definition.
'reliable' is the first definition.
(I've seen this in another clue)
'racket' is the second definition.
(I know that racket is a more specific form of the action make noise)
(Other definitions for sound that I've seen before include "strait" , "Reliable - noise" , "Not diseased or damaged - listen" , "Valid" , "Measure depth" .)