Ask a person for leave (6)
I believe the answer is:
begone
'leave' is the definition.
'ask a person' is the wordplay.
'ask' becomes 'beg' (begging is a kind of asking).
'a person' becomes 'one'.
'beg'+'one'='BEGONE'
'for' acts as a link.
(Other definitions for begone that I've seen before include "Get away" , "make himself scarce" , "Take a hike" , "get lost" , "Archaic command to buzz off" .)