Excellent victories give rise to taxation (7,5)
I believe the answer is:
capital gains
'rise to taxation' is the definition.
I can't tell whether this definition defines the answer.
'excellent victories' is the wordplay.
'excellent' becomes 'capital' (I've seen this before).
'victories' becomes 'gains' (I am not sure about this - if you are sure you should believe this answer much more).
'capital'+'gains'='CAPITAL GAINS'
'give' is the link.
Can you help me to learn more?
(Other definitions for capital gains that I've seen before include "target of 17, 8 [CHANCELLORS STATEMENT] - with 6a" , "must happen when money flows into London" , "Profits from investment sales" , "Profit" , "post-war Honolulu and Juneau for US?" .)