Green’s Dictionary of Slang

(UK Und.) to supply officers with information about a robbery and then warn the thieves to get away; thus n. an informer for both sides.

1859		Matsell Vocabulum 65: pear To draw supplies from both sides; to give the officers information, and then tell the thieves to get out of the way.
1895		C. Crowe Aus. Sl. Dict. 56: Pear, one who gives information to police and thieves, and manages to get pay from both parties.