Knightly means of saving face (5)

I believe the answer is:

visor

I'm a little stuck... Click here to teach me more about this clue!

'means of saving face' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

(Other definitions for visor that I've seen before include "piece of armour" , "Means of saving face" , "Peak of a cap" , "Sunshade" , "Moveable piece of helmet" .)

I've seen this clue in the Evening Standard.

Want a hint initially instead of a full solution? Install my app