Yep will be the belt!
You can re-tension it but that wont last long. Best to replace it. They only cost a fiver from ECP. (£4.82) Make sure you get the correct one as it depends if you have air-con or not!
Fairly simple job but has to be done from underneath as you have to drop the undertray anyway.
Also do check the fluid level.
I did this to mine recently and made a big difference to the steering!
On my 4th belt in 7 years, so that shows they need regular attention.