What a visor may prove to be? (9)

'what a visor may prove' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'be?' is the wordplay.
I cannot quite understand how this works, but
'be?' could be 'face' (facing is a kind of being) and 'face' is located in the answer.
The remaining letters 'saver' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).

'to' is the link.

Can you help me to learn more?