Finance sport to a good end (4)
I believe the answer is:
fund
'finance' is the definition.
(I've seen this before)
'sport to a good end' is the wordplay.
'sport' becomes 'fun' ('fun' can be a synonym of 'sport'**).
'end' indicates one should take the final letters.
The final letter of 'good' is 'd'.
'fun'+'d'='FUND'
(Other definitions for fund that I've seen before include "Stock, resources" , "Cash reserve" , "Capitalize" , "Provide with money, say project" , "Monetary resources" .)