Unhappy child, heir we spoiled as long as possible (4,2,3,4)
I believe the answer is:
down to the wire
'heir we spoiled as long as possible' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'unhappy child' is the wordplay.
I cannot really see how this works, but
'unhappy' could be 'down' (down can mean sad) and 'down' is present in the answer.
'child' could be 'tot' (term for a young child) and 'tot' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for down to the wire that I've seen before include "Up to the very last moment" , "approaching deadline" .)