Whatever happens, customs inspector may look here! (2,3,4)
I believe the answer is:
in any case
'whatever happens' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for in any case that I've seen before include "Besides" , "Whatever the facts are, one way or the other" , "Where customs officers may search" , "Where a customs officer may search" , "At all events" .)