1: Arcking shot from Bill O'Brien (3)
2: Former leader's relative with bit of tension in stomach (4, 3)
3: Cross chest located in New York (5)
4: Sounds like a bright child (3).
5: Organized fatso follows start of precise measurement including pound of seasoning (11)
6: Overhear them speak of the serpent's purpose. (9)
7: Vanity items go wild (7)
8: Lepers treated by North Dakota specialist? Brilliant! (11)
11: Left with pal carrying new gold case (11)
12: Be prepared with amnesties for truancy (11)
15: Fur from hormone treatment I took - it's mortifying (4,5)
18: Carry on after New York's flipped into unconsciousness (7)
20: Warned of related crackpot (7)
23: Oak's first seen on the first of May with its leaves out (5)
25: Ran into a section of the time-table (3)
27: Cot is unmade for short month in fall (3)