Theban plays fail to make peaceful appeal (3,3,4)
I believe the answer is:
ban the bomb
'peaceful appeal' is the definition.
(slogan by the Campaign for Nuclear Disarmament)
'theban plays fail' is the wordplay.
'plays' is an anagram indicator.
'fail' becomes 'bomb' (synonyms).
'theban' with letters rearranged gives 'banthe'.
'banthe'+'bomb'='BAN THE BOMB'
'to make' acts as a link.
(Other definitions for ban the bomb that I've seen before include "disarming message" , "pacifist's slogan" .)