Representative from Spain - girl with a case of rivalry (8)
I believe the answer is:
emissary
'representative' is the definition.
(emissary is a kind of representative)
'spain girl with a case of rivalry' is the wordplay.
'spain' becomes 'e' (abbreviation for Espana).
'girl' becomes 'miss' (I've seen this before**).
'with' is a charade indicator (letters next to each other).
'case of' says to hollow out the word (remove centre letters) (outsides of).
'rivalry' with its centre removed is 'ry'.
'e'+'miss'+'a'+'ry'='EMISSARY'
'from' acts as a link.
(Other definitions for emissary that I've seen before include "Diplomatic messenger" , "Someone sent on a mission" , "Delegate" , "Government messenger" , "one dispatched officially" .)