Possible Clues:

• Two characters going after 1 (not Turner) in shop
• Give up to the police
• Act as The Informer in part allocated selflessly
• Be a fink to
• Double-cross, maybe
• Betray no sailor in uprising
• A number alongside pitch turned grass up
• Expose by blabbing
• Betray by finking
• Betray first sign of ruthlessness, a heavyweight