Affair which follows case of criminal racket (7)
I believe the answer is:
clamour
'racket' is the definition.
(I've seen this before)
'affair which follows case of criminal' is the wordplay.
'affair' becomes 'amour' (amour can mean a love affair).
'which follows' says to put letters next to each other.
'case of' means to remove the middle letters (outsides of).
'criminal' with its middle removed is 'cl'.
'amour' put after 'cl' is 'CLAMOUR'.
(Other definitions for clamour that I've seen before include "Loud and persistent outcry" , "Loud noise of shouting" , "Uproar" , "Loud confused noise" , "Noisy disturbance" .)