Settling endless dispute could be foolish (6)
I believe the answer is:
stupid
'foolish' is the definition.
(I know that foolish can be written as stupid)
'settling endless dispute' is the wordplay.
'settling' indicates anagramming the letters (settle can mean to solve or sort out).
'endless' means to remove the last letter.
'dispute' with its final letter taken off is 'disput'.
'disput' is an anagram of 'STUPID'.
'could be' acts as a link.
(Other definitions for stupid that I've seen before include "bovine" , "Crass" , "(Seeming to be) lacking intelligence" , "Ignorant" , "Imbecilic" .)