Financially effective (8)
I believe the answer is:
economic
'financially effective' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for economic that I've seen before include "Comic one giving a good return for money laid out" , "Monetary; cost-effective" , "Likely to bring a profit" , "Sparing in the use of resources" , "Using the minimum resources necessary for effectiveness" .)