Alter ego Tees announces setting 23 1 Across — for starters — in 18 (3,5)

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

HOT GATES ( THERMOPYLAE (entry at 18 across) means HOT GATES . The name is derived from its hot sulphur springs. In Greek mythology the HOT GATES is one of the entrances to Hades)