Throws, around lord, protective barriers (7)
I believe the answer is:
shields
'protective barriers' is the definition.
(shield can mean a protective barrier or screen)
'throws around lord' is the wordplay.
'throws' becomes 'shies' (shy is a kind of throw).
'around' is an insertion indicator.
'lord' becomes 'ld' (abbreviation for the aristocratic title).
'shies' going around 'ld' is 'SHIELDS'.
(Other definitions for shields that I've seen before include "Escutcheons" , "Protects or hides from danger" , "More than one buckler, maybe" .)