This puzzle proved easier for me on the whole than others by Bradman. I still struggled to complete the last couple of clues (3D, 11A) though. And there is one answer I trust I have right but where I do not understand the wordplay (2D).

Across
1. AUGMENT - AUGUST with “US” replaced by “MEN”. A nice replacement clue with a great surface.
5. REDACT - RED (Communist) + ACT (legislation)
8. CHARGRILL - A (a) + R (right) + G (good) in CHILL (cool)
9. RELIC - ELI (priest) in RC (Catholic)
11. AMICE - A (a) + MICE (rodents). I may have come across this word before but I had to use my dictionary to get it.
12. ART SCHOOL - anagram of CHARTS + LOO (room) backwards
13. ON STREAM - anagram of A MONSTER
17. TROUGH - THROUGH with H (one hospital) dropped
19. GUJERATI - JUG (prison taking a wrong turn) + anagram of IRATE. This is a new spelling to me.
22. ROTATABLE - ROTA (list) + TABLE (item of furniture)
23. NYMPH - NY (American location) + MPH (speed)
24. XHOSA - X (unknown) + HOS[e]A. How nice to see an X as a checked letter!
25. TRATTORIA - AI (excellent) + ROT (tripe) + TART (sweet) all backwards
26. BEAKER - A (a) + K (king) in BEER (drink)
27. NUMERAL - NUM (union) + ERA (time) + L (line). This stumped me for a while — my mind would not think of the right type of union.

Down
1. ARCHAEOPTERYX - anagram of OX PRAY TEACHER. I got this easily and that gave me a good start.
2. GOALIES - ? I do not understand the wordplay here
3. EAGRE - EAGER (keen) with the last two letters reversed (final somersault). An eagre is a bore, that is in the sense of a large wave.
4. TRIMARAN - TRIM (good condition) + ARAN (Irish islands)
5. RELATE - RE (in connection with) + LATE (previous)
6. DIRECTIVE - RECTI (muscles) in DIVE (activity at pool)
7. CALL OUT - A (a) + L (learner) in CLOUT (smack)
10. CALL ME ISHMAEL - anagram of EMAIL SCAM HELL
14. RIGHT BANK - RIGHT (conservative) + BANK (financial institution)
16. SUZERAIN - SUEZ (canal) half-changed + RAIN (water coming down)
18. OUTCOME - OUT (unfashionable) + CO (firm) + ME (this person)
20. ADMIRER - anagram of MARRIED. This is an anagram I have come across before.
21,15: OBITER DICTUM - O (nothing) + anagram of IM DIRECT BUT. I was unaware of this phrase but guessed DICTUM as the second word and then looked up the rest.
23. NOTUM - NO (lack of) + TUM (stomach). The notum is the upper part of the thorax of an insect. In spite of the fact that I was once an amateur entomologist, I had never come across this word.