The old fools made gibes about a saint (7)
I believe the answer is:
'the old fools' is the definition.
'jesters' can be an answer for 'fools' ('jester' can be a synonym of 'fool'). I am not sure about the 'the old' bit.
'gibes about a saint' is the wordplay.
'gibes' becomes 'jeers' ('jeer' can be a synonym of 'gibe').
'about' indicates putting letters inside.
'a saint' becomes 'st' (abbreviation).
'jeers' placed around 'st' is 'JESTERS'.
'made' acts as a link.
Can you help me to learn more?
(Another definition for jesters that I've seen is " Jokers".)