Contract's ending: request job (4)
I believe the answer is:
task
'job' is the definition.
(I know that job can be written as task)
'contract's ending request' is the wordplay.
'ending' indicates one should take the final letters (the ending of the word).
'request' becomes 'ask' (to ask is to request something).
The final letter of 'contract' is 't'.
't'+'ask'='TASK'
(Other definitions for task that I've seen before include "Burden with work" , "Set piece of work" , "Assignment" , "something to do" , "Sort of force" .)