How do I solve 12 across in Daily Telegraph Cryptic 3371?

Question

Accepted Answer

12 across reads "Tray he soiled, dirty" (6 letters); the answer is EARTHY. It's an anagram clue: the answer is a rearrangement of letters supplied by the clue itself. Look for an indicator like 'mixed', 'broken', 'cooked', or 'wild', and find a phrase whose letters add up to the answer's length. The full step-by-step breakdown is on this page.

Tray he soiled, dirty (6)

12A — Tray he soiled, dirty (6) — EARTHY