Burden of work papers (7)

I believe the answer is:

oppress

I'm a little stuck... Click here to teach me more about this clue!

'burden' is the definition.
(I've seen this in another clue)

I cannot understand how the rest of the clue works.

(Other definitions for oppress that I've seen before include "Crush, subjugate" , "Treat harshly" , "Distress" , "Burden" , "Keep in subjection and hardship" .)

I've seen this clue in The Sun and The Times.

Want a hint initially instead of a full solution? Install my app