Very large keys have split: but they can be fixed (4)
I believe the answer is:
odds
'can be fixed' is the definition.
I can't judge whether this defines the answer.
'very large keys have split but they' is the wordplay.
I cannot really see how this works, but
'keys' could be 'dd' (two D's - as in the musical key of D) and 'dd' is present in the answer.
'large' could be 'os' (abbreviation for oversize) and 'os' is located in the remaining letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for odds that I've seen before include "inequality" , "Betting figures" , "at which one may be disagreeing" , "Betting price" , "Measure of probability" .)