Artist turns over extract on time (5)
I believe the answer is:
klimt
'artist' is the definition.
(I know that Klimt is a painter)
'turns over extract on time' is the wordplay.
'turns over' is a reversal indicator.
'extract' becomes 'milk' (milking is a kind of extracting).
'on' means one lot of letters go next to another.
'time' becomes 't' (abbreviation).
'milk' backwards is 'klim'.
'klim'+'t'='KLIMT'
(Other definitions for klimt that I've seen before include "Gustav -, nineteenth to twentieth century Austrian painter" , "Austrian artist" , "Austrian painter influenced by Art Nouveau" , "Gustav - - , Austrian symbolist" .)