How do I solve 23 down in Express Cryptic 20260519?

Question

Accepted Answer

23 down reads "Unusual case for experts" (4 letters); the answer is ACES. 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.

Unusual case for experts (4)

23D — Unusual case for experts (4) — ACES