Vegetate with bad posture and no energy (6)
I believe the answer is:
sprout
'vegetate' is the definition.
(thesaurus)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for sprout that I've seen before include "Spring up like vegetable from Brussels" , "Bud; a type of cabbage" , "Put forth shoots" , "Begin to develop" , "Start growing" .)