Where you might find prisoner from Peru, once? (5)
I believe the answer is:
incan
This clue might be a double definition.
'where you might find prisoner' is the first definition.
The definition suggests a singular noun which matches the answer.
'from peru once?' is the second definition.
(Other definitions for incan that I've seen before include "ancient civilization" , "doing time?" , "Of an Andean civilisation overthrown by Pizarro in 1533" , "Of an ancient Andean culture" , "Of ancient Peruvians" .)