Artist using mud mostly and egg! (4)
I believe the answer is:
miro
'artist' is the definition.
(I've seen this before)
'mud mostly and egg' is the wordplay.
'mud' becomes 'mire' (synonyms).
'mostly' means to remove the last letter (most but not all of the word).
'and' says to put letters next to each other.
'egg' becomes 'o' (an 'o' resembles an egg).
'mire' with its final letter taken away is 'mir'.
'mir'+'o'='MIRO'
'using' acts as a link.
(Other definitions for miro that I've seen before include "Joan --, Spanish artist" , "He painted" , "Catalan artist" , "Joan -, twentieth century Spanish surrealist painter" .)