Outstanding ring joined with another (4)
I believe the answer is:
owed
'outstanding' is the definition.
('owed' can be a synonym of 'outstanding')
'ring joined with another' is the wordplay.
'ring' becomes 'o'.
'joined with another' becomes 'wed'.
'o'+'wed'='OWED'
(Other definitions for owed that I've seen before include "Outstanding" , "Was indebted" , "to be paid" , "Had a duty to pay" , "Had an obligation to pay" .)