Anonymous female star, not so great (8)
I believe the answer is:
faceless
'anonymous' is the definition.
(similar in meaning)
'female star not so great' is the wordplay.
'female' becomes 'f' (abbreviation).
'star' becomes 'ace' (synonyms).
'not so great' becomes 'less' (inferior or lesser).
'f'+'ace'+'less'='FACELESS'
(Other definitions for faceless that I've seen before include "Anonymous" , "Unidentified - lacking personal distinction" , "Without identity or character - from the front?" , "Unidentifiable" .)