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I have given this further thought, and on consideration, with apologies to Catron, I actually think that GET THE POINT fits the clue better than SEE THE POINT, as the purpose of a sheath is obviously to prevent the dagger sticking into its owner, rather than conceal the blade.
It will be interesting to see what the actual answer is, and I imagine, one way or another, a lot of entrants will be disappointed, which is a shame because the real problem is not that the clue is obscure, but the phrasing is simply lazy.