One fibber pursuing endless stardom, so common (8)
I believe the answer is:
familiar
'common' is the definition.
('familiar' can be a synonym of 'common')
'one fibber pursuing endless stardom' is the wordplay.
'one' becomes 'i' (Roman numeral).
'fibber' becomes 'liar' (I've seen this before).
'pursuing' is a charade indicator (letters next to each other).
'endless' means to remove the last letter.
'stardom' becomes 'fame' (I've seen this before).
'fame' with its final letter removed is 'fam'.
'i'+'liar'='iliar'
'iliar' put after 'fam' is 'FAMILIAR'.
'so' acts as a link.
(Other definitions for familiar that I've seen before include "Well-known witch's cat" , "Au fait" , "Conversant with the witch's cat?" , "Well-acquainted with a witch's cat" , "Well-known like witch's assistant" .)