Green’s Dictionary of Slang

1. (UK Und.) a thief, a pickpocket.

1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue n.p.: Cloyes, thieves, robbers.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.

2. see cly n. (2)