Painter in Arles is fed drink periodically (5)
I believe the answer is:
ernst
'painter' is the definition.
(Max Ernst)
'arles is fed drink periodically' is the wordplay.
'arles' becomes 'est' (I can't justify this - if you can you should believe this answer much more).
'is fed' means one lot of letters goes inside another (one word is 'fed' to another).
'periodically' means one should take alternating letters (letters must be selected 'every so often').
The alternating letters of 'drink' are 'rn'.
'est' enclosing 'rn' is 'ERNST'.
'in' is the link.
(Other definitions for ernst that I've seen before include "German-born painter, Max, co-founder of dadaism, d. 1976" , "Max --, German painter" , "artist's name" , "Young partner" , "Max -, twentieth century German Surrealist artist" .)