Shun or attack (6)

I believe the answer is:

onrush

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'shun or attack' is the definition.
I can't tell whether this definition defines the answer.

'shun or attack' is the wordplay.
'attack' indicates an anagram.
'shun'+'or'='shunor'
'shunor' is an anagram of 'ONRUSH'.

Can you help me to learn more?

(Other definitions for onrush that I've seen before include "Forward charge of Hurons" , "Attack" , "sudden swoop" , "Forceful forward flow" , "Career" .)

I've seen this clue in The Irish Independent.

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