Most ill-advised, if nothing else (9)
I believe the answer is:
leastwise
'if nothing else' is the definition.
(I've seen this before)
'most ill-advised' is the wordplay.
'most ill' becomes 'least' (I can't justify this - if you can you should give a lot more credence to this answer).
'advised' becomes 'wise' (associated in meaning).
'least'+'wise'='LEASTWISE'
Can you help me to learn more?
(Other definitions for leastwise that I've seen before include "in Hollywood at any rate" , "However (US)" , "in any case" , "anyway" , "If nothing else" .)