Protection, quiet, that is given to Lord briefly (6)
I believe the answer is:
shield
'protection' is the definition.
(I know that shield is a type of protection)
'quiet that is given to lord briefly' is the wordplay.
'quiet' becomes 'sh' (both can be said to tell someone to be quiet).
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'given to' says to put letters next to each other.
'lord briefly' becomes 'ld' (abbreviation for the aristocratic title; 'briefly' indicates a short form).
'sh'+'ie'+'ld'='SHIELD'
(Other definitions for shield that I've seen before include "Is held (anag.)" , "Protective structure or device" , "Protect, screen" , "Piece of armour carried on arm to protect body" , "Protective covering" .)