In favour of parent ditching husband for impresario (8)
I believe the answer is:
promoter
'impresario' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
(Other definitions for promoter that I've seen before include "Organiser eg of boxing" , "One who stages boxing matches etc" , "Organiser (of a sporting event)" , "Impresario" , "One putting on a sporting event" .)