Alright for a Greek character to have an animal (5)
I believe the answer is:
'an animal' is the definition.
'alright for a greek character' is the wordplay.
'alright' becomes 'ok' ('OK' can be a synonym of 'alright').
'for' says to put letters next to each other.
'greek character' becomes 'pi' (letter from the Greek alphabet).
'to have' is the link.
(Other definitions for okapi that I've seen before include "Giraffe-related mammal" , "Giraffe-like animal with stripes" , "Hoofed mammal" , "Mammal of giraffe family" , "Ruminant related to the giraffe" .)