Whatever happens, there's a cocktail in a can, yes? (2,3,4)
I believe the answer is:
in any case
'whatever happens' is the definition.
(I've seen this before)
'a cocktail in a can yes?' is the wordplay.
'a cocktail' is an anagram indicator.
'in'+'a'+'can'+'yes'='inacanyes'
'inacanyes' is an anagram of 'IN ANY CASE'.
'there's' is the link.
(Other definitions for in any case that I've seen before include "At all events" , "Lawyers may be so employed" , "Where customs officers may search" , "Whatever the facts are, one way or the other" , "Whatever the facts are, whatever happens" .)