Nothing with us is unsettled (3)
I believe the answer is:
owe
'is unsettled' is the definition.
I can't tell whether this definition defines the answer.
'nothing with us' is the wordplay.
'nothing' becomes 'O' (looks like zero - 0).
'with' is a charade indicator (letters next to each other).
'us' becomes 'we' ().
'o'+'we'='OWE'
Can you help me to learn more?
(Other definitions for owe that I've seen before include "have favours to return" , "Be in the red" , "Be in debt - woe is me" , "Have a debt to (someone)" , "Have obligation to pay" .)