Girl attending a festival (4)
I believe the answer is:
gala
'festival' is the definition.
(thesaurus)
'girl attending a' is the wordplay.
'girl' becomes 'gal' ('gal' can be a synonym of 'girl'**).
'attending' says to put letters next to each other.
'gal'+'a'='GALA'
(Other definitions for gala that I've seen before include "Carnival, fete" , "A festive occasion, perhaps of sporting nature" , "field day" , "Jamboree" , "Fête" .)