The unambitious seem to be more stable (9)
I believe the answer is:
shiftless
'the unambitious' is the definition.
(thesaurus)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for shiftless that I've seen before include "Like an automatic American car" , "Idle" , "lacking in initiative" , "Lazy - indolent" .)