this may be obvious to some of you… but here goes.
i'm currently running a 32 tooth single ring up front on my santa cruz superlight, with xt cranks. wondering what sort of chain guide will fit my frame/ crankset?
what's all this 'iscg fitting' lark? ❓

a dérailleur will work. ISCG tabs are threaded mounts around the BB shell to enable a guide to be fitted, and no, your superlight doesn't have them.

but you can buy externally mounted bb iscg adaptors which sit between the bb cup and the frame and replace one of the spacers (assuming your using hollowtech 2 cups?). I use one of these on my prince albert. looks like this –>

Or you can buy some chain devices that are actually bb mounted themselves.

http://www.chainreactioncycles.com/Models.aspx?ModelID=40904

Try one of these, if you can get it.

Jim