Current drop
Hi Tony R welcome to the forum. under powering electronic items is possible, but very much dependent on the application, its never a good idea to drop power below rated levels, this strains the circuit, you should aim to power any item with in safe power levels, some under powering will degrade and destroy some components, try and stick to the rated power levels needed, but and not loosely some apps can be under powered, depending on the applications.
Dave.