Green’s Dictionary of Slang

yet to be adj.

[rhy. sl.]

free (both of behaviour and of cost).

[UK]G. Kersh Fowlers End (2001) 268: On the Johnny Horner I must stand / In this land of the yet-to-be, / ’Olding out my Martin’s-le-Grand / For the price of a Rosie Lee.
[UK]Dodson & Saczek Dict. of Cockney Rhy. Sl.