Old Peruvians going to the capital of Ecuador as a precaution (2,4)
I believe the answer is:
in case
'as a precaution' is the definition.
(just in case)
'old peruvians going to the capital of ecuador' is the wordplay.
'old peruvians' becomes 'incas' (I've seen this before).
'going to' says to put letters next to each other.
'the capital of' suggests taking the first letters.
The initial letter of 'ecuador' is 'e'.
'incas'+'e'='IN CASE'
(Other definitions for in case that I've seen before include "For fear that" , "In order to allow for eventualities" , "Packed" , "Where traveller may keep clothes" , "As a precaution" .)