Is it ensure, insure, or assure?
also pot-boiler, 1864 in the figurative literary sense, from pot (n.1) + agent noun from boil (v.). The notion is of something one writes solely to put food on the table.
A book, play, etc, written just to get money, esp something done rather badly by a writer who can do very well
[1864+; fr the notion that one does such work only to keep the food pot boiling in the domicile]