is it possible at all to use a flash with a hotshoe plug on a canon powershot a70?

Just looked at canon website, and I don't think you could as there is nowhere to connect a flash to. That being said, if you had another flash that could work as an external slave, the onboard flash might trigger that flash using a control flash eye, that detects a flash and triggers the flash it is connected to.

Others will correct me if I am wrong I am sure.