Giraffes' cousins fine, needing a short wee (6)

I believe the answer is:

okapis

But I can't explain it at all!

(Other definitions for okapis that I've seen before include "African mammals" , "Ok, Pa is wrong about the giraffe-type animals" , "Relatives of the giraffe" , "They're similar to the giraffes but smaller" , "Giraffe-like creatures" .)

I've seen this clue in The Guardian.

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