How do I solve 7 down in Times Cryptic 29531?

Question

Accepted Answer

7 down reads "Twinkling star aircrew noted at certain frequency" (5 letters); the answer is TRICE. 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.

Twinkling star aircrew noted at certain frequency (5)

7D — Twinkling star aircrew noted at certain frequency (5) — TRICE