Flies prophet across South American capital (10)
I believe the answer is:
mosquitoes
'flies' is the definition.
(I've seen this before)
'prophet across south american capital' is the wordplay.
'prophet' becomes 'moses' (Moses is an example).
'across' is an insertion indicator.
'south american capital' becomes 'quito' (capital of Ecuador).
'moses' enclosing 'quito' is 'MOSQUITOES'.
(Other definitions for mosquitoes that I've seen before include "Carriers of disease" , "Malaria carriers" , "Flies" , "Bearers of malaria" , "Irritating fliers" .)