I need to do a format but my computer won’t recognise my Clip even though I’ve put music on using same computer.
If it is one of the newer models (Clip+ or Clip Zip), the player can format itself (Settings > System Settings > Format). However, this may not solve your connectivity issue. Have you tried a diffferent USB port, cable or computer?
If you really want to check the files using your computer, you need to set this as USB mode. The link from the Sandisk KB site should be able to guide you here. 
http://kb.sandisk.com/app/answers/detail/a_id/207/~/verifying-and-changing-the-usb-mode-of-the-device-to-msc-or-mtp
