Everything is about some girl: Lily? (9)
I believe the answer is:
amaryllis
'lily?' is the definition.
(lily is a type of amaryllis)
'everything is about some girl' is the wordplay.
'everything' becomes 'all' (all things).
'about' indicates putting letters inside.
'some girl' becomes 'mary' (girl's name).
'all'+'is'='allis'
'allis' enclosing 'mary' is 'AMARYLLIS'.
(Other definitions for amaryllis that I've seen before include "Sly alarm I turn on for the flower" , "Large-flowered bulb" , "Bulb with showy flowers" , "Plant with showy flowers - I rally Sam (anag)" , "Showy bulbous plant" .)