Green’s Dictionary of Slang

the preparation of a cup of tea, or meal.

1921		N&Q 12 Ser. IX 425: Drum-Up (A).The act of collecting from several chums various ingredients to make a savoury extra meal.
1932		F. Jennings Tramping with Tramps 37: I strayed into a roadside coppice to have a simple lunch and a drum-up of tea.
1939		J. Worby Spiv’s Progress 8: Having in a drum up, mate?