Scale of corporation that employs a million (5)
I believe the answer is:
gamut
'scale' is the definition.
(I know that gamut is a type of scale)
'corporation that employs a million' is the wordplay.
'corporation' becomes 'gut' (both can humorously mean belly fat).
'that employs' is an insertion indicator.
'million' becomes 'm' (abbreviation).
'a'+'m'='am'
'gut' going around 'am' is 'GAMUT'.
'of' is the link.
(Other definitions for gamut that I've seen before include "Full (emotional) range" , "Whole range (from A to Z)" , "Ambit" , "Entire range" , "Complete range (of something)" .)