Retain it if review shows it to be compatible (3,2)

I believe the answer is:

fit in

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'compatible' is the definition.
(I've seen this before)

I can't explain the remainder of the clue.

(Other definitions for fit in that I've seen before include "Make room for; be acceptable" , "compatible" , "Find time for" , "Not be out of place" , "Conform after adjustment" .)

I've seen this clue in The Irish Times.

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