how can i export a bank statement from clear books to excel

You can't per se - it's something that really needs implementing though, should come as standard.

What you can do is highlight/copy all items, paste into Notepad (to remove all formatting) then copy/paste over into Excel. You might have to quickly play around with the column headers and delete a pointless column or two but it's do'able as a workaround.

Alternatively, go to Reports > Transactions. Select the appropriate bank account from the 'account' dropdown, select the to/from dates you want it to cover and click find. You'll then be presented with a report that can be exported into excel or PDF. Only downside is it doesn't come with a running balance (which i'm sure you could rectify in Excel with a quick formula if needed).

I personally use the Notepad route, takes all of 30 seconds once you've done it a few times.