Govern with cruelty and injustice (7)
'govern with cruelty and injustice' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for oppress that I've seen before include "Treat tyrannically" , "Subdue" , "'Persecute, come down heavy on (7)'" , "Keep in subjection and hardship" , "Govern cruelly" .)
(Other definitions for oppressed that I've seen before include "Burdened, physically or mentally" , "Downtrodden" , "Worried or subjugated" , "Tormented" , "Kept in subjection" .)