1: Climp up on horse on high ground (5)
2: Unappealing environment for a snooze (3)
3: Nut hounds famed Arizona shooter for something to deaden the noise (7)
4: ...near fishing boats stocked with cold bait (5,8)
5: Fish spawn upstream in little orifices (3)
6: Washed-up press agent, having dropped client's butt, is not the one in the driver's seat (9)
8: Dine out and stop being vague (13)
9: Get rid of the botched act, dearie (9)
11: Central Slovak airport damaged 16-down (9)
12: Call for help oddly stops (3)
14: E.g., lead Boston finally out of cellar, American League (4,5)
17: Going after the final piece of puzzle for a very long time (3)
18: Usually regret about loss follows start of stint in AA (2,1,4)
21: Some unpretentious language! (5)
23: One final, huge Greek goddess (3)