Racket for when one is playing? (5)
I believe the answer is:
noise
'racket' is the definition.
(racket can mean a loud noise)
'one is playing?' is the wordplay.
'playing?' is an anagram indicator.
'one'+'is'='oneis'
'oneis' with letters rearranged gives 'NOISE'.
'for when' is the link.
(Other definitions for noise that I've seen before include "Loud or disturbing sound" , "Kind of pollution" , "Virgil's birthplace" , "Sound of any kind" , "Unwanted sound" .)