Leave a fib for keeper (6)
I believe the answer is:
goalie
'for keeper' is the definition.
(I've seen this before)
'leave a fib' is the wordplay.
'leave' becomes 'go' (to go is to depart or leave).
'fib' becomes 'lie' (a fib is a lie).
'go'+'a'+'lie'='GOALIE'
(Other definitions for goalie that I've seen before include "Hart perhaps" , "Football player" , "Netkeeper, in short" , "Footballer" , "Football team member" .)