Food is extravagant that fills half the room (7)
I believe the answer is:
risotto
'food' is the definition.
(risotto is a kind of food)
'is extravagant that fills half the room' is the wordplay.
'extravagant' becomes 'ott' (I've seen this in other clues).
'that fills' indicates putting letters inside.
'half' means to take half the letters.
'is'+'ott'='isott'
'room' halved is 'ro'.
'isott' put inside 'ro' is 'RISOTTO'.
(Other definitions for risotto that I've seen before include "Savoury rice dish" , "Perhaps Italian" , "Italian course" , "Main course" , "F" .)