On a back of a page from an appointment book, there are a set of cryptic messages. On the front is an appointment to visit the zoo, but it is crossed out with the notation "Not enough!"

1. They hit the lofty pavement, for they fear that place, also this place (6)
2. Sixty minutes is the limit of our wait to go to nine locations very quickly (6)
3. Would-be gourds and spice trees cascade and bounce among the uncultivated (7)
4. Trio sits on new device to stroke a solitary snout (6)
5. This planet makes me sneeze; I'll pick you up (4)
6. A rough sextet labors to keep feathers dry (5)
7. For any journey, antlers are preferable to a valise (3)
8. Wandering on sandy hills, singing of odd things in a minor key (7)
9. Utility in lesser bodies of water is inedible (13)
10. Insufficient residential space breeds theft and paranoia (4)
11. Large darkness from a little thing, and vice versa(8)
12. Great resounding in a watery cave -- it's an aphorism (5)
13. Easy to play alluring sounds for burrow-dweller? Just the opposite! (5)
14. Submarine ledge is home to constant preoccupation with reversal (8)
15. Altitudinous moisture is cetacean in origin (3)