Takes advantage of customs (4)
I believe the answer is:
uses
I believe this is a double definition.
'takes advantage' is the first definition.
(I've seen this in other clues)
'customs' is the second definition.
(I know this)
'of' is the link.
(Other definitions for uses that I've seen before include "'Purposes, functions (4)'" , "Utilises" , "Employs" , "manipulates" , "Puts into service" .)