What's wrong with my car? Clunking at front left side. Could it be my brakes?

I have a ford fiesta zetec. Like an idiot I did not run it for a few months after getting a flat tyre. I had the tyre replaced today and used my cover with green flag to get a guy out to recharge my battery as it was completely flat.

The bloke who changed the tyre said the brake stuck but had released when he changed the tyre. (right drivers side)

However when I set off in the car earlier I noticed a clunking sound from the front left side (sort of with each rotation) and so I went straight back and parked it. I could feel the brake pedal moving as I hovered my foot in time with the clunks.

Is it likely to be a rusted brake?

Advice would be great!

Check the engine.

Yes. It is damage to the surface of the brake disc or drum.
It may wear smooth after a few applications of the brakes at a decent speed (not necessarily high speed, but 20-30mph), or you may need to replace the disc or drum.