Persist as a mythical reptile (6)
I believe the answer is:
dragon
'mythical reptile' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for dragon that I've seen before include "Creature of Teutonic mythology" , "It's red on the Welsh flag" , "particularly intimidating woman" , "Fiery monster" , "Continue interminably" .)