Star in East, twinkling, seen by chance (8)
I believe the answer is:
asterisk
'star' is the definition.
('asterisk' can be a synonym of 'star')
'east twinkling seen by chance' is the wordplay.
'twinkling' is an anagram indicator.
'seen by' is a charade indicator (letters next to each other).
'chance' becomes 'risk' ('risk' can be a synonym of 'chance'**).
'east' anagrammed gives 'aste'.
'aste'+'risk'='ASTERISK'
'in' is the link.
(Other definitions for asterisk that I've seen before include "Sign" , "Footnote marker" , "Star-shaped character used in printing" , "Star for the printer" , "Star-like symbol as reference mark" .)