Just read your first post again and you say its only when the clutch starts to engage.

That sounds more like perhaps the plate is wearing down to the rivets.

Does it feel like the clutch is about to give up?

When you sit there with the engine running and your foot fully on the clutch does it whine then?
Also when in neatral and you lift off the clutch does it do it then? Or only when a gear is selected?