Where smugglers might hide contraband, whatever happens (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 "Where customs officers may search" , "Besides" , "Whatever the facts are, whatever happens" , "No matter what" , "Whatever the facts are, one way or the other" .)