How do I solve 1 across in Express Cryptic 20260524?

Question

Accepted Answer

1 across reads "One's vain, and it’s a problem" (5 letters); the answer is POSER. 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.

One's vain, and it’s a problem (5)

1A — One's vain, and it’s a problem (5) — POSER