Remove obstacle from a foreign advertisement (6)
I believe the answer is:
unplug
'remove obstacle' is the definition.
(eg unplugging a drain)
'a foreign advertisement' is the wordplay.
'a foreign' becomes 'un' ('a' translated into French).
'advertisement' becomes 'plug' (a plug is an advert for something).
'un'+'plug'='UNPLUG'
'from' is the link.
(Other definitions for unplug that I've seen before include "Disconnect (kettle or toaster?)" , "Take out of socket" , "Remove a blockage from" , "Remove from a socket" , "Remove power from" .)