Degenerate artist meets knave on vacation (4)
I believe the answer is:
rake
'degenerate' is the definition.
(rake can mean an immoral man)
'artist meets knave on vacation' is the wordplay.
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'meets' means one lot of letters go next to another.
'on vacation' means to remove the middle letters (after the inside letters have vacated the word).
'knave' with its centre taken out is 'ke'.
'ra'+'ke'='RAKE'
(Other definitions for rake that I've seen before include "Progress was visualised for one" , "Implement for a debauched person" , "Gardening tool for the dissolute fellow" , "this to smooth the way?" , "set at an angle" .)