American game investigators (8)
I believe the answer is:
checkers
I believe this is a double definition.
'american game' is the first definition.
(I've seen this before)
'investigators' is the second definition.
(checker is a kind of investigator)
(Other definitions for checkers that I've seen before include "Draughts in America" , "American game" , "those on board" , "They scrutinise" , "Quality assurance personnel" .)