Crossword Genius

A fair exchange in sight (2,3,3,2,3)

Ross

I believe the answer is:

an eye for an eye

I'm a little stuck... Click here to teach me more about this clue!

'exchange in sight?' is the definition.
I know nothing about this answer so I cannot tell whether this works.

'a fair' is the wordplay.
I cannot quite understand how this works, but
'a' could be 'an' and 'an' is located in the answer.
The remaining letters 'eyeforaneye' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?

(Other definitions for an eye for an eye that I've seen before include "Retribution" , "Retaliation principle (2,3,3,2,3)" , "The law of retaliation (2,3,3,2,3)" , "an exchange of views?" , "Retaliation in kind" .)

I've seen this clue in The Globe and Mail and The Irish News.
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