More fully developed American departing to make amends for going north (5)

I believe the answer is:

riper

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'more fully developed' is the definition.
(I've seen this in another clue)

I cannot understand how the remainder of the clue works.

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(Other definitions for riper that I've seen before include "More mature and ready to be eaten" , "More harvestable" , "More ready for picking" , "More ready to pick" , "Maturer" .)

I've seen this clue in The Times.

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