How do I solve 13 down in Times Cryptic 29548?

Question

Accepted Answer

13 down reads "Mushroom left ring after ring after ring" (10 letters); the answer is PORTOBELLO. It's a charade: the answer breaks into parts in clue order, each part clued by a word or short phrase. No indicators needed; watch for standard abbreviations (RA = artist, US = American, IN = at home) and short synonyms. The full step-by-step breakdown is on this page.

Mushroom left ring after ring after ring (10)

13D — Mushroom left ring after ring after ring (10) — PORTOBELLO