Artist seen in mailroom every now and then (4)
I believe the answer is:
miro
'artist' is the definition.
(I've seen this before)
'mailroom every now and then' is the wordplay.
'every now and then' indicates alternate letters (letters selected at regular intervals).
The alternate letters of 'mailroom' are 'MIRO'.
'seen in' acts as a link.
(Other definitions for miro that I've seen before include "Joan -, twentieth century Spanish surrealist painter" , "He painted" , "Joan --, Spanish artist" , "Catalan artist" .)