Green’s Dictionary of Slang

ale and porter v.

[the contrasting colours of the two beers, light and dark]

(UK Und.) to mix legitimate work with thieving.

[UK]Manchester Eve. News 16 Oct. 4/1: I might do a bit o’ ‘ale and portering’ (working and thieving) [...] A little bit of work, hawking or otherwise, with a spice of thieving.