The Spanish agent has turned smart (7)
I believe the answer is:
elegant
'smart' is the definition.
(similar in meaning)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for elegant that I've seen before include "Chic; smart" , "Stylish in appearance, a gentle kind" , "Cleverly simple" , "Attractive and graceful or stylish" , "Handsome" .)