John -, first American to orbit the Earth in space (5)

I believe the answer is:

glenn

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'john' is the definition.
(I've seen this in another clue)

I cannot understand how the rest of the clue works.

(Other definitions for glenn that I've seen before include "John -, first US astronaut to orbit the earth" , "John -, first American to orbit the earth" , "John --, pioneer US astronaut" .)

I've seen this clue in The Times.

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