The most common and most likely answer to this crossword clue is the 8 letter word ANTELOPE
I've seen this crossword clue in The Daily Telegraph
A
N
T
E
L
O
P
E
More clues leading to the result ANTELOPE
- Rod reversed in before animal
- One moving fast from Dinant, eloper
- Animal bound to go after some chips
- Bovid mammal bound to be tied to stake
- Animal: one leapt out
- 12 awkwardly holding cut beast
- Fast runner in leading position backed, covered by stake
- They progress in leaps and bounds before eating cane up
- Stake cut head of elegant creature
- Held by Durante, lop-eared animal
Buddy explains!

The straight part
We know that "Vegetarian" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case vegetarian = antelope.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does ANTELOPE mean?
ANTELOPE noun- Any of several African mammals of the family Bovidae distinguished by hollow horns, which, unlike deer, they do not shed.
- The pronghorn, Antilocapra americana.
- A fierce legendary creature said to live on the banks of the Euphrates, having long serrated horns and being hard to catch.