A guard to face (5)

I believe the answer is:

visor

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'a guard' is the definition.
(a visor is a guard for one's eyes)

I can't explain the remainder of the clue.

(Other definitions for visor that I've seen before include "Eyeshade" , "Anti-glare flap over the windscreen" , "piece of armour" , "Sunshade" , "Screen to filter glare" .)

I've seen this clue in The Globe and Mail and The Irish Independent.

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