Region over in Canada is Alberta (4)
I believe the answer is:
asia
'region' is the definition.
(I have seen 'populous region' mean 'asia' so perhaps 'region' could also mean 'asia')
'over in canada is alberta' is the wordplay.
'over' says the letters should be written backwards.
'in' says the answer is hidden in the clue.
'aisa' can be found hidden inside 'canada is alberta'.
'aisa' back-to-front is 'ASIA'.
(Other definitions for asia that I've seen before include "Populous continent" , "The nations of the East, collectively" , "Largest land-mass" , "Eastern continent" , "Stretch of land" .)