Put to work, some decades until going into retirement (4)
I believe the answer is:
used
'put to work' is the definition.
(I've seen this in another clue)
'some decades until going into retirement' is the wordplay.
'some' indicates taking the first letters.
'going' becomes 'es' (I can't justify this - if you can you should believe this answer much more).
'into' is an insertion indicator.
'retirement' says the letters should be written backwards (retire can mean to return or go back).
The initial letters of 'decades until' is 'du'.
'du' going around 'es' is 'desu'.
'desu' reversed gives 'USED'.
Can you help me to learn more?
(Other definitions for used that I've seen before include "like majority of cars?" , "Was treating" , "Utilised" , "Employed in task, or second-hand" , "Worn" .)