Simon is upset by this job (7)
I believe the answer is:
mission
'this job' is the definition.
(a mission is a job or task)
'simon is upset' is the wordplay.
'upset' indicates an anagram.
'simon'+'is'='simonis'
'simonis' is an anagram of 'MISSION'.
'by' acts as a link.
(Other definitions for mission that I've seen before include "Journey with a specific purpose" , "Assignment - calling" , "Vocation; embassy" , "Ministry sent by a church to spread its teaching" , "Assignment; expedition" .)