Some good, misleading surfaces today with a few different anagram indicators, eg ‘building’, ‘created’, ‘rocking’ and ‘bumping’.
There were two unfamiliar words, 13a and 14d, which unfortunately intersected, and the latter needed a knowledge of German, or access to a German dictionary, to complete the wordplay which was perhaps a little unfair for those solving the puzzle during their daily commute.
Across
8 PORTIA P (quietly) *(RIA[l]TO)
9 WINE GUMS W (Welsh) M[arketing] in *(GENIUS)
10 ETNA [spum]ANTE reversed
11 ROTISSERIE ROT (rubbish) IS S[ome] ERIE (lake)
12 DAUB D[ecorator] AU (gold) B (black)
13 MANGOSTEEN *(ON STAGE) in MEN (staff)
17 PEER dd
18 NERVE hidden in ‘runNER VEering’
19 RICH *(CH[a]IR)
21 LADY GODIVA LAD (kid) Y[ank] G[o-kart] *(AVOID)
23 IBEX BI (twice) reversed EX (late)
24 KENNEL CLUB cd
28 NIKE KIN (family) reversed [hous]E[hold]
29 REHEARSE EARS (organ’s) in *(HERE)
30 NOSH-UP H (hospital) in NO SUP (drink)
Down
1 BOAT RACE dd
2 STRAWBERRY WARTS (marks) reversed homophone of ‘Bury’ (somewhere in Lancashire)
3 SACRAMENTO RA (artist) MEN (folk) in *(COATS)
4 TWIT TWI[s]T (succeeded avoiding 60s dance)
5 ONUS [b]ONUS (introduction of baby leaves extra)
6 OGLE OGrE (man-eater) with ‘r’ changed to L
7 UMPIRE RIP (split) in EMU (bird) reversed
14 NURMI NUR (only, in German) MI[le] – Paavo Nurmi, 1920s middle and long distance runner
15 ONE-MAN BAND *(NAME ON ) BAND (tape)
16 TURGIDNESS *(TRUDGES IN) S[tifling]
20 CHECKOUT HECK (fancy) in CO (company) U[pmarke]T
22 AXEMEN A[irfield] X (10) MEN E (English) MEN (troops)
25 NEEP PEE (wee) N[ursery) reversed
26 LYRE L (learner) RY (tracks) reversed E (electronic)
27 LIEU LIE (rest) U (university)