Politically diverse assembly in no-win situation, liable to fall apart (6)
I believe the answer is:
untied
'liable to fall apart' is the definition.
(not secured or tied together)
'politically diverse assembly in no-win situation' is the wordplay.
'politically diverse assembly' becomes 'un' (I am not sure about this - if you are sure you should believe this answer much more).
'in no-win situation' becomes 'tied' (tied without a winner).
'un'+'tied'='UNTIED'
Can you help me to learn more?
(Other definitions for untied that I've seen before include "Picked loose" , "Unfastened, unlaced" , "'Unfastened, lace say (6)'" , "Not fastened" , "No longer bound" .)