Foreigner on top of the world? (4)
I believe the answer is:
pole
I believe this is a double definition.
'foreigner' is the first definition.
'top of the world?' is the second definition.
(I've seen this in another clue)
'on' is the link.
(Other definitions for pole that I've seen before include "flag-bearer" , "possibly exerting a powerful attraction?" , "Round rod of wood or metal" , "Limit" , "'Round rod, of wood say (4)'" .)