All right, a Greek character follows the animal (5)
I believe the answer is:
Here is my best explanation:
'the animal' is the definition.
(I've seen this before)
'all right a greek character follows' is the subsidiary indication.
'all right' becomes 'ok' ('ok' can be a synonym of 'all right'**).
'greek character' becomes 'pi'.
'follows' is a charade indicator (letters next to each other).
(Other definitions for okapi that I've seen before include "Animal related to giraffe", "Ruminant related to the giraffe", "Mammal of giraffe family", "Giraffe-like mammal", "Central Afr. ruminant", "One of the giraffe family", "Wild animal", "Giraffe family mammal", "Animal, a sort of zebra/giraffe cross" and "Giraffe family member".)