Hold down round power iron (7)

I believe the answer is:

oppress

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'hold down' is the definition.
Although both the answer and definition are verbs in their base form, I cannot understand how one could define the other.

'round power iron' is the wordplay.
'round' becomes 'o' (round can mean a round object).
'power' becomes 'p'.
'iron' becomes 'press' (I've seen this before).
'o'+'p'+'press'='OPPRESS'

Can you help me to learn more?

(Other definitions for oppress that I've seen before include "Vitality" , "Distress" , "Hold down cruelly" , "Trample down" , "Treat tyrannically" .)

I've seen this clue in the Sydney Morning Herald.

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