Asteroid ᠅

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Solve 3 / 4 clues to proceed.

Satellite imagery showed close-up, frequently (fortunate, not practical) (4)
(Ulam and Thue–Morse) proposal stipulates: lullabies influence somniloquists’ withdrawal headrest (6)
(Composite of Alcuin)’s students can’t cut back examination of diving gear (5)
Wrote a love letter, e.g., with opening (square words of the Constitution) (5)