Celebration: feature originally of summer in the States (8)
I believe the answer is:
festival
'celebration' is the definition.
(I know that celebration can be written as festival)
'feature originally of summer in the states' is the wordplay.
'originally of' says to take the initial letters (I've seen 'originally' mean this).
'summer in the states' becomes 'estival' (I've seen this before).
The initial letter of 'feature' is 'f'.
'f'+'estival'='FESTIVAL'
(Other definitions for festival that I've seen before include "Holy day" , "Lift vase (anag.)" , "Joyful celebration" , "Live fast (anag.)" , "Carnival or jamboree" .)