Applicant's back with request for job (4)
I believe the answer is:
task
'for job' is the definition.
(synonyms)
'applicant's back with request' is the wordplay.
'back' says to take the final letters (the letter at the back).
'with' means one lot of letters go next to another.
'request' becomes 'ask' (to ask is to request something).
The final letter of 'applicant' is 't'.
't'+'ask'='TASK'
(Other definitions for task that I've seen before include "Arduous bit of work" , "Difficult piece of work" , "Job, undertaking" , "Chore, job." , "Give mission" .)