The ones that involved one in the racket (5)
I believe the answer is:
noise
'the racket' is the definition.
('noise' can be a synonym of 'racket')
'the ones that involved one in' is the wordplay.
'the ones' becomes 'is' ('I' can be a synonym of 'one').
'that involved' indicates anagramming the letters (involved can mean confusing or complex).
'in' is an insertion indicator.
'one' anagrammed gives 'noe'.
'is' going into 'noe' is 'NOISE'.
(Other definitions for noise that I've seen before include "Unwelcome sound" , "Static - sound" , "interference" , "Clatter" , "Kind of pollution" .)