Class or group of antelopes out East (5)
I believe the answer is:
genus
'class' is the definition.
(I've seen this before)
'antelopes out east' is the wordplay.
'antelopes' becomes 'gnus' (gnu is a kind of antelope).
'out' means one lot of letters goes inside another.
'east' becomes 'e' (synonyms).
'gnus' enclosing 'e' is 'GENUS'.
'or group of' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for genus that I've seen before include "species grouped together" , "Taxonomic class between family and species" , "Taxonomic group (biol.)" , "Latin class?" , "Part of the family" .)