Artist performing in opera company (5)
I believe the answer is:
monet
'artist' is the definition.
(painter Claude Monet)
'performing in opera company' is the wordplay.
'performing' becomes 'on' (as in being on stage).
'in' is an insertion indicator.
'opera company' becomes 'met' (I've seen this before).
'on' put into 'met' is 'MONET'.
(Other definitions for monet that I've seen before include "Claude -, French artist" , "Claude ---, painter (waterlilies)" , "Claude, impressionist painter, d. 1926" , "'Water Lilies' 13ac" , "French artist shown in ..." .)