My business runs (3)
I believe the answer is:
cor
'my' is the definition.
(both are expressions of surprise)
'business runs' is the wordplay.
'business' becomes 'co' (short for company).
'runs' becomes 'r' (cricket abbreviation).
'co'+'r'='COR'
(Other definitions for cor that I've seen before include "Expression of surprise" , "Surprised expression" , "Gosh" , "Blimey" .)