Possible Clues:

• Visor worn by card-players
• Energy certainly possessed by English guard
• Croupier's headgear
• Poker player's topper
• Cover for some sleepers
• Visor from east English certainly possessed first
• Sleeper's aid
• Guard protecting those doing the spying gets to look cool
• Visor certainly owned, see, though not at first, on the periphery
• Consent obtained in Beeb, essentially, for protection from glare