A girl superstar full of sex-appeal (5)
I believe the answer is:
susan
'a girl' is the definition.
(I've seen this before)
'superstar full of sex-appeal' is the wordplay.
'superstar' becomes 'sun' (I can't justify this - if you can you should believe this answer much more).
'full of' is an insertion indicator.
'sex appeal' becomes 'sa'.
'sun' placed around 'sa' is 'SUSAN'.
Can you help me to learn more?
(Other definitions for susan that I've seen before include "woman" , "- - Sarandon (films)" , "When lazy, she's a revolving tray on a dining table" , "-- Howatch, novelist" , "female" .)