ACROSS
1. <rock band> NICKELBACK ⇒ ←NI←
7. <greasers> OILS = _O_I_L_S_
9. DESI ←DENG← = DESIGNED <planned>
10. U + RENT outside G = URGENT <pressing>
11. <straight> HETERO = THERE* O
12. <acquiring a lot of> RAKING IN = R_ + AKIN GIN
13. <ball> MASQUERADE = MADE outside SQUARE*
15. <reservoir> SUMP = SUM P
17. <portico> STOA = O A after ST
18. <big cheese> PANJANDRUM = PAN J + AND RUM
20. (.r)TER RACE D(o.) = TERRACED <with steps>
22. DI + GIT'S = DIGITS <contact information>
24. KELP IE = KELPIE <malevolent water spirit>
25. _OL_ I G ARCH = OLIGARCH <tycoon>
26. <inspected> EYED = "IDE"
27. <silly> SOFT-HEADED = (.t)S OF THE AD ED(i.)

DOWN
2. EGLANTINE* = INELEGANT <not cultivated>
3. ←INK← + FE = KNIFE <blade>
4. LI NEON E + SOCKET'S outside P = LINE ONE'S POCKETS <to save money>
5. (RADAR ON)* = ANDORRA <location in the Pyrenees>
6. (DUNK CHICKEN + SLAW)* = KNUCKLE SANDWICH <punch>
7. <directed> ORGANISED = GRANDIOSE*
8. L_ U_ N_ G_ I_ = LUNGI <sarong>
14. <animal> QUADRUPED = QUAD outside DRUPE
16. <perhaps walrus> MOUSTACHE = (ATE SO MUCH)*
19. <begin sleeping> NODS OFF = ←DON← SO FF
21. _E_N_E + MY = ENEMY <rival>
23. <fruit> GUAVA = G_ U_ A_ V_ A_