The most common and most likely answer to this crossword clue is the 8 letter word THEROPOD
T
H
E
R
O
P
O
D
Buddy explains!

The straight part
We know that "Dinosaur" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dinosaur = theropod.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 THEROPOD mean?
THEROPOD noun- Any bipedal dinosaur, of the suborder Theropoda, from the Jurassic and Cretaceous periods.