Ipod frozen- can't reset

After I updated my IPod touch 5th gen to IOS 9.1 it's frozen on an app(BBC Iplayer- which still works, I just can't close it). My home screen button is broken so I can't hard reset and when I plug it into itunes it says 'Trust this computer' but nothing comes up on the ipod-presumably because it's frozen.

It still charges and notifications come through, I just can't open them. Think I need to reset it and re-install the software but not sure how to do this?