How do I solve 13 across in Daily Telegraph Cryptic 31243?

Question

Accepted Answer

13 across reads "Smack rear in flamenco dance" (5 letters); the answer is TANGO. It's a letter-selection clue: take specific letters from a longer source. 'First of' means the opening letter, 'extremely' means first + last, 'regularly' means every other letter, 'oddly' / 'evenly' means odd or even positions. The full step-by-step breakdown is on this page.

Smack rear in flamenco dance (5)

13A — Smack rear in flamenco dance (5) — TANGO