Gift on bill — pay finally (6)
I believe the answer is:
legacy
'gift' is the definition.
(a legacy is gifted to future generations)
'on bill pay finally' is the wordplay.
'on' becomes 'leg' (cricket term, fielding positions).
'bill' becomes 'ac' (short for account).
'finally' indicates one should take the final letters.
The final letter of 'pay' is 'y'.
'leg'+'ac'+'y'='LEGACY'
(Other definitions for legacy that I've seen before include "What is left to one in will" , "Sort of gift" , "Like old software" , "Gift of property by will" , "That which is handed down by a predecessor" .)