Go work in post office, collecting fines (3,3)
I believe the answer is:
pop off
'go' is the definition.
(I know that go can be written as pop off)
'work in post office collecting fines' is the wordplay.
'work in' becomes 'op' (operation, work done in an operating theatre. I am not sure about the 'in' bit.).
'post office' becomes 'po' (abbreviation).
'collecting' is an insertion indicator.
'fines' becomes 'ff' (an abbreviation for fine written twice).
'op' put inside 'po' is 'popo'.
'popo'+'ff'='POP OFF'
Can you help me to learn more?
(Other definitions for pop off that I've seen before include "Go" , "Leave without warning" , "Die informally to sound of champagne cork?" , "Die informally like champagne cork?" , "exit" .)