ACROSS
 7. <Japanese warrior> RONIN = (.d)RON IN(s.)
 8. <pure> UNALLOYED = U (ONLY + LEAD)*
11. <bumbling> SHAMBOLIC = SHAM ←LOB← IC
12. <extra> BONUS = ONUS after B
13. <dry> ARID = A_ R_ ID
14. <representatives> DELEGATION = GA inside DELETION
17. SUB MEN + U = SUBMENU <more options>
18. <soldier> TROOPER = ←REPORT← outside _O_
20. R E_ O_ inside STEPSIS = STEREOPSIS <depth perception>
21. <marine mammal> ORCA = O_R _C_A_
22. OS AKA = OSAKA <port city>
24. (ISN'T HE)* + OUP = IN THE SOUP <struggling>
26. BALL DEER outside A = BALLADEER <songster>
27. "GARNER" = GHANA <somewhere in West Africa>

DOWN
 1. TRES PASS = TRESPASS <offence>
 2. <wanting more> INSATIABLE = BANALITIES*
 3. <cut> SNUB = ←BUNS←
 4. QUELL ←RUSE← + PRISE = QUELLE SURPRISE <what a shock for Robespierre!>
 5. <French city> LYON = YON after L_
 6. ODD + SON = ODDS-ON <probably>
 9. ANC IE N_ THIS TORY = ANCIENT HISTORY <no longer relevant>
10. LABOR outside RAD = LABRADOR <part of Canada>
15. <businesslike> IMPERSONAL = (.r)IMPERS ON AL(l.)
16. (MEAD + RARE)* = DEMERARA <cane sugar>
19. + REAP, PEAR = REAPPEAR <come back>
20. S C_ OO BY = SCOOBY <clue>
23. <competent> ABLE = "ABEL"
25. <as omelette> EGGY = EG G_Y