Dope invested in account having yen for business (6)
I believe the answer is:
agency
'business' is the definition.
(agency is a kind of business)
'dope invested in account having yen' is the wordplay.
'dope' becomes 'gen' (I've seen this in other clues).
'invested in' indicates putting letters inside.
'account' becomes 'ac'.
'having' means one lot of letters go next to another.
'yen' becomes 'y'.
'gen' inserted into 'ac' is 'agenc'.
'agenc'+'y'='AGENCY'
'for' acts as a link.
(Other definitions for agency that I've seen before include "Travel ..., advertising..., employment" , "Function of one who acts for another" , "See 24 Across" , "Business that acts for actors" , "Government office" .)