Royal Iberian drained orangeade (7)
I believe the answer is:
infanta
'royal' is the definition.
(I've seen this before)
'iberian drained orangeade' is the wordplay.
'drained' says to hollow out the word (remove centre letters).
'orangeade' becomes 'fanta' (brand of fizzy orange drink).
'iberian' with its centre taken out is 'in'.
'in'+'fanta'='INFANTA'
(Other definitions for infanta that I've seen before include "Spanish monarch's daughter" , "Royal personage" , "Formerly, the daughter of a Spanish king" , "Historically, a daughter of the Spanish king - sounds very young" , "King's daughter" .)