Calls island on Shetland to begin with (5)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

YELL (island, one of the North Isles in Shetland, off the northern coast of Scotland) + beginning letter of S [hetland]. I don’t think Shetland is doing double duty because “island” is enough to define Yell. “On Shetland” is a little odd because Shetland isn’t a single island but an archipelago; “in Shetland” would be more natural.