A girl getting into giddy hero-worship? (9)
I believe the answer is:
adoration
'hero-worship?' is the definition.
(I've seen this before)
'a girl getting into giddy' is the wordplay.
'a girl' becomes 'adora' (**).
'getting' means one lot of letters go next to another.
'giddy' indicates anagramming the letters.
'into' with letters rearranged gives 'tion'.
'adora'+'tion'='ADORATION'
(Other definitions for adoration that I've seen before include "high regard" , "Hero-worship" , "high esteem" , "Deep love and respect" , "passionate allegiance" .)