Pterosaur or archaeopteryx gathered around sky lights (6)
I believe the answer is:
aurora
'sky lights' is the definition.
(I've seen this in another clue)
'pterosaur or archaeopteryx gathered around' is the wordplay.
'around' indicates the answer is hidden within the clue.
'AURORA' is hidden within 'pterosaur or archaeopteryx gathered'.
(Other definitions for aurora that I've seen before include "Roman Godess of the Dawn" , "Display of lights in the night sky" , "Northern or southern lights" , "Polar light show" , "Roman goddess of the dawn" .)