More than one large animal represented in horse? Not entirely (6)
I believe the answer is:
rhinos
'more than one large animal' is the definition.
(rhino is short for rhinoceros)
'represented in horse? not entirely' is the wordplay.
'represented' is an anagram indicator.
'not entirely' means to remove the last letter.
'in'+'horse'='inhorse'
'inhorse' with its last letter taken away is 'inhors'.
'inhors' is an anagram of 'RHINOS'.
(Other definitions for rhinos that I've seen before include "Horned mammals" , "Massive mammals with one or two horns, in short" .)