Personal claim which turns sour (4)
I believe the answer is:
ours
'personal claim' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'turns sour' is the wordplay.
'turns' indicates anagramming the letters.
'sour' is an anagram of 'OURS'.
'which' is the link.
Can you help me to learn more?
(Other definitions for ours that I've seen before include "Relating or belonging to us" , "Yours and mine!" , "Indiscriminate slaughter" , "British" , "The French bear" .)