Three clues put me in a nautical mood so I found this plain sailing with a following wind and fair tide. My voyage took only 7:05 so I'd hardly had time to break out the G&Ts.
1. Tries again at rear of mule train (8)
REHEARSE - tries again - REHEARS, MUL(E).
5. Animal in forest, a gazelle (4)
STAG - in foreST A Gazelle.
8. Be suspicious of party, but relaxed.
DOUBT - party - DO, anagram (relaxed) of BUT.
9. Briefly board ship prior to travel ban (7)
EMBARGO - briefly board ship - EMBAR(k), travel - GO.
11. Have a meal, warm, without husband (3)
EAT - warm without husband - (h)EAT.
12. Doctor and MA having part in complex procedure (9)
RIGMAROLE - doctor - RIG (fix), MA, part - ROLE.
13. Colas I ordered for party (6)
SOCIAL - anagram (ordered) of COLAS I. I needed checkers for this.
15. Drawing of small sailing vessel (6)
SKETCH - small - S, sailing vessel - KETCH.
18. Justify being very mean (6)
VINDICATE - very - V, mean - INDICATE. Looked this up as I wasn't entirely happy about vindicate=justify. I thought that vindicate was more 'prove right'. However Collins has justify as a synonym in the sense of support - the report vindicated his policy.
19. Cut fruit, then vegetable (3)
PEA - cut fruit - PEA(r).
20. Daily in circulation, originally thinner (7)
CLEANER - (C)irculation, thinner - LEANER.
21. Leading group capsized (5)
UPSET - leading - UP, group - SET.
22. Draw a circle round item of jewellery (4)
RING - double definition.
23. Make light of losing on stage show (4,4)
PLAY DOWN - losing - DOWN on/after stage show - PLAY.
1. Set right about frock (7)
REDRESS - about - RE, frock - DRESS.
2. Search round a place frequently visited (5)
HAUNT - search - HUNT round a - A.
3. Conservative blocking amendment causes heated dispute (11)
ALTERCATION - conservative - C blocking/inside amendment - ALTERATION.
4. Toboggan beginning to slide over projecting shelf (6)
SLEDGE - (S)lide over projected ting shelf - LEDGE.
6. Come about act available (4,3)
TURN OUT - act - TURN, available - OUT - the latest film is out.
7. Good to wander in small wooded area (5)
GROVE - good (G), wander - ROVE.
10. A dark horse in the field of children's literature (5,6)
BLACK BEAUTY - cryptic definition.
14. Business worry (7)
CONCERN - double definition.
16. Cheer that woman catching a number (7)
HEARTEN - that woman - HER catching a - A, number - TEN.
17. Save about a litre in cask (6)
BARREL - save - BAR - all bar one, about - RE, litre - L.
18. Member of the clergy visiting Civic Arena (5)
VICAR - in ciVIC ARena.
19. Bother with duck sauce (5)
PESTO - bother - PEST with duck - O.