The prompt is "there's a secret key to this puzzle." The clues for 5A5ABoost someone else's 280-character message, say[-----] and 7A7A180 degrees from NW[-----] are for the two-letter answers RT and SE. But the full entries are REMIT5ABoost someone else's 280-character message, say[-----] / SNORE7A180 degrees from NW[-----]. The unclued "secret" letters, in grid order, are EMINOR, which is a musical key, and the meta answer.