Extremely engaging android evokes expression of surprise (4)

I believe the answer is:

egad

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'expression of surprise' is the definition.
(I've seen this in another clue)

I can't explain the remainder of the clue.

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(Other definitions for egad that I've seen before include "Christ" , "Forgotten curse" , "Oath sworn" , "traditional oath" , "Mild oath - aged (anag)" .)

I've seen this clue in The Irish Times.

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