Frustration caused by senior cop's job (14)
I believe the answer is:
disappointment
'frustration' is the definition.
(I've seen this before)
'senior cop's job' is the wordplay.
'senior cop's' becomes 'di's' (detective inspector).
'job' becomes 'appointment' (appointment is a kind of job).
'dis'+'appointment'='DISAPPOINTMENT'
'caused by' acts as a link.
(Other definitions for disappointment that I've seen before include "Let-down" , "Setback" , "Frustration" , "unhappiness" , "Frustrating thing" .)