Once having got cheeky with the master (6)
I believe the answer is:
expert
'the master' is the definition.
(I've seen this before)
'once having got cheeky' is the wordplay.
'once' becomes 'ex'.
'having got' is a charade indicator (letters next to each other).
'cheeky' becomes 'pert' (I've seen this before**).
'ex'+'pert'='EXPERT'
'with' is the link.
(Other definitions for expert that I've seen before include "Adept" , "Buff" , "Clever" , "Person with special knowledge or ability" , "One has specialist knowledge or ability" .)