Tired? Don't lean so much! (8)
I believe the answer is:
listless
'tired? don't' is the definition.
The answer and definition are different parts of speech. However, adjectives and past participle verbs sometimes mean the same thing.
'lean so much' is the wordplay.
'lean' becomes 'list' (both can mean to tilt).
'so much' becomes 'less' (I can't explain this - if you can you should give a lot more credence to this answer).
'list'+'less'='LISTLESS'
Can you help me to learn more?
(Other definitions for listless that I've seen before include "disorganised on a shopping trip?" , "Tells sis to be lacking in energy" , "(unlike Ko-Ko)" , "Languid - apathetic" , "without enthusiasm" .)