Gives the green light to reviewing segments of The Waste Land (4)

I believe the answer is:

lets

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'gives' is the definition.
(letting is a kind of giving)

I don't understand the rest of the clue.

(Other definitions for lets that I've seen before include "Leases" , "we shall serve them again!" , "Rents out or allows" , "Yes" , "Allows or causes to" .)

I've seen this clue in the Irish Times and the Irish Times (Crosaire).

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