Green’s Dictionary of Slang

a window-cleaner.

1958		Listener 20 Nov. 818/2: His fellow shiners disregarded the L.C.C. by-law, because very few windows are equipped with metal hooks for holding on a safety belt .
1967		Sun. Times 8 Jan. 3/7: Len is widely regarded as London’s top ‘shiner’ (window cleaner) .
1977		Centuryan (Office Cleaning Services) Christmas 1/1: There we were, shiners and cleaning ladies, surrounding Fred and Dora on the float by the London Wall [OED].