Make the crook become better (4,3,6)
I believe the answer is:
turn the corner
'make the crook' is the definition.
I don't know anything about this answer so I can't tell whether this works.
'become better' is the wordplay.
I cannot really see how this works, but
'become' could be 'turn' (synonyms) and 'turn' is located in the answer.
The remaining letters 'thecorner' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for turn the corner that I've seen before include "What driver at T-junction might do next" , "Start to improve" , "Get past the worst" , "Pass a critical point and improve" , "Begin to get better" .)