Disloyal fellow facing crisis after losing power (6)
I believe the answer is:
fickle
'disloyal' is the definition.
(thesaurus)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for fickle that I've seen before include "Liable to sudden unpredictable change" , "Inconstant in affections" , "Often changing, not constant or loyal" , "Often changing, not reliable emotionally" , "Erratic, unpredictable" .)