Not necessarily correct (14)
I believe the answer is:
overcompensate
'not necessarily correct' is the definition.
'overcompensate' can be an answer for 'correct' (overcompensating is a kind of correcting). I'm not sure about the 'not necessarily' bit.
'necessarily correct' is the wordplay.
'necessarily' becomes 'over' (I can't explain this - if you can you should give a lot more credence to this answer).
'correct' becomes 'compensate' (synonyms).
'over'+'compensate'='OVERCOMPENSATE'
Can you help me to learn more?
(Other definitions for overcompensate that I've seen before include "Go too far in trying to correct a fault" , "Pay too much" , "More than satisfy" .)