Sun, in Santiago (3)
I believe the answer is:
sol
'sun in santiago' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sol that I've seen before include "Note; Peruvian currency" , "The Sun (or Campbell?)" , "Personification of the sun" , "Spanish and poetic sun" , "Roman sun-god" .)