Green’s Dictionary of Slang

a watchman.

a.1796		‘The Court of Equity’ in Farmer Merry Songs and Ballads (1897) IV 283: That coachman Dow, and clocky Brown.
1821		W.T. Moncrieff Tom and Jerryy II ii: Good night, old Clockey.
1825		‘All England Now are Slanging It’ Universal Songster I 39/2: I beg pardon, clocky, but you see I’m a little deginerated in my faculties to-night.
1835		G. Kent Modern Flash Dict. 10: Clockey, a watchman.
1848		Flash Dict. in Sinks of London Laid Open.