Maxim used in Gilead agenda (5)
I believe the answer is:
adage
'maxim' is the definition.
(I've seen this before)
'in gilead agenda' is the wordplay.
'in' says the answer is hidden in the clue.
'ADAGE' can be found hidden inside 'gilead agenda'.
'used' acts as a link.
(Other definitions for adage that I've seen before include "Slogan" , "Saying, saw" , "Proverb expressing a general truth" , "say it again and again!" , "Saw, proverb" .)