eland
kudu
Oribi is a small African antelope
gnu
dik-diks Dikdik
dik dik
The dik-dik is a small African antelope that lives for months with no water except for dew and the moisture in its diet of vegetation.
A three letter African antelope is the "gnu", which ends in a "u" not a "you". The more common name for the gnu is the wildebeeste, but that won't fit into your crossword puzzle.
Buffalo is not really an antelope, but it is the closest relative to the antelope where the name ends with an o.
calf (baby antelope)
African Wiled Donkey
Ted
Thompson gazelle