High-flyer seen in southern Ecuador (4)
I believe the answer is:
erne
'high-flyer' is the definition.
'in southern ecuador' is the wordplay.
'in' says the answer is hidden in the clue.
'ERNE' can be found hidden inside 'southern ecuador'.
'seen' acts as a link.
(Other definitions for erne that I've seen before include "'Sea-eagle, river and lough (4)'" , "Fish-eating sea eagle" , "one that catches fish?" , "Flier" , "Sea eagle and Northern loch" .)