How do I solve 29 across in Daily Telegraph Cryptic 31253?

Question

Accepted Answer

29 across reads "Lewis for one is extremely louche" (4 letters); the answer is ISLE. 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.

Lewis for one is extremely louche (4)

29A — Lewis for one is extremely louche (4) — ISLE