Reptile's fear understood when picked up (9)
I believe the answer is:
'reptile's' is the definition.
(pterosaur is a kind of reptile)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for pterosaur that I've seen before include "Fossil flying reptile" , "very old flier" , "Extinct flying reptile" , "ancient flyer" , "Old reptile" .)