In the main, as a rule (9)
I believe the answer is:
generally
I believe this clue is a double definition.
'in the main' is the first definition.
(thesaurus)
'as a rule' is the second definition.
('as a rule' means generally or typically)
(Other definitions for generally that I've seen before include "In most cases, usually" , "Usually, as a rule" , "most of the time" , "as usual" , "For the most part" .)