How do I solve 21 down in Daily Telegraph Cryptic 3372?

Question

Accepted Answer

21 down reads "Fire jacket" (6 letters); the answer is BLAZER. It's a double-definition clue: two separate definitions of the same word sit side by side. No wordplay split and no indicators — both halves of the clue define the answer. The full step-by-step breakdown is on this page.

Fire jacket (6)

21D — Fire jacket (6) — BLAZER