ACROSS
1. PORT "RICHER" = PORTRAITURE <painting>
7. BIPEDAL* = PIEBALD <with black and white coloration>
8. ←C(-r)I(-m)B(-o)← = BIC <commonplace stationery brand>
9. <did spring> LEAPT = LEA P T
11. ←U FANS← = SNAFU <military omnishambles>
12. RAC + ED = RACED <sped>
14. <dwarf planet> SEDNA = ←ANDES←
15. "SPAR" = SPA <place intended for relaxation>
16. <curry> BIRYANI = ←I + NAY RIB←
18. <inciting populist anger> DEMAGOGUING = (DEMO outside AG) (GLUING - L)

DOWN
1. (EPIDURAL OPS)* = POPULARISED <made more accessible>
2. <regret> RUE = "ROO"
3. <banter> ROAST = (A SORT)*
4. <river> INDUS = D inside (IN US)
5. (PB RAID) under U = UPBRAID <reprimand>
6. <optimistic> ENCOURAGING = (NCO ARGUING*) under E
10. <hail> ACCLAIM = A CC LIMA*
13. (DEBUT - T) G = DEBUG <fix problems in implementation>
14. <young person> SPRIG = S PRIG
17. <tropical fish> AHI = (-t)AHI(-ti)