Straighten things out with father's brother, in short, bringing him around old city (6)
I believe the answer is:
uncurl
'straighten' is the definition.
(I've seen this before)
'out with father's brother in short bringing him around old city' is the wordplay.
I cannot really see how this works, but
'around' could be 'c' (abbreviation for 'circa') and 'c' is found within the answer.
'city' could be 'ur' (ancient Sumerian city state) and 'ur' is located in the answer.
This explanation may well be incorrect...
'things' is the link.
Can you help me to learn more?
(Another definition for uncurl that I've seen is " Straighten from rolled up position".)