Possibly over in Chile, by a mountain (5)
'possibly' is the definition.
('maybe' can be a synonym of 'possibly')
'over in chile by a mountain' is the wordplay.
'over' says the letters should be written backwards.
'in' indicates a hidden word.
'ebyam' is hidden within 'chile by a mountain'.
'ebyam' backwards is 'MAYBE'.
(Other definitions for maybe that I've seen before include "Perhaps, might happen", "Perhaps, possibly".)