Artist, a master at reticulation (5)
I believe the answer is:
manet
'artist' is the definition.
(I've seen this before)
'a master at reticulation' is the wordplay.
'a master' becomes 'ma'.
'at' means one lot of letters go next to another.
'reticulation' becomes 'net' ('net' can be a synonym of 'reticulation').
'ma'+'net'='MANET'
(Other definitions for manet that I've seen before include "artistic individual" , "Edouard ___, painted Dejeuner sur l'herbe, d. 1883" , "Painter of Le Dejeuner sur l'herbe, d. 1883" , "Edouard -- (artist)" , "Edouard - - (painter)" .)