How a sale should be organised, all things considered (2,1,5)
I believe the answer is:
as a whole
'all things considered' is the definition.
(thesaurus)
'how a sale should be organised' is the wordplay.
'should be organised' indicates an anagram.
'how'+'a'+'sale'='howasale'
'howasale' with letters rearranged gives 'AS A WHOLE'.
(Other definitions for as a whole that I've seen before include "completely" , "In general" .)