Withdraw defence group, for example (5)

I believe the answer is:

unsay

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'withdraw' is the definition.
(I know that withdraw can be written as unsay)

'defence group for example' is the wordplay.
'defence group' becomes 'un' (I can't justify this - if you can you should give a lot more credence to this answer).
'for example' becomes 'say' ('say' can be used to introduce an example).
'un'+'say'='UNSAY'

Can you help me to learn more?

(Other definitions for unsay that I've seen before include "Recall" , "Take back (words)" .)

I've seen this clue in The Daily Express.

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