A job done for nothing? (9,4)

'a job done for nothing?' is the definition.
I know nothing about this answer so I can't tell whether this works.

'job done for nothing?' is the wordplay.
I cannot really understand how this works, but
'job' could be 'task' (synonyms) and 'task' is present in the answer.
'done' could be 'u' and 'u' 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?