Immature artist and wife (3)
I believe the answer is:
raw
'immature' is the definition.
(I've seen this before)
'artist and wife' is the wordplay.
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'and' means one lot of letters go next to another.
'wife' becomes 'w' (abbreviation).
'ra'+'w'='RAW'
(Other definitions for raw that I've seen before include "Uncooked or sore" , "Damp and chilly" , "Uncooked; immature" , "Not processed" , "Untried (of recruit) - uncooked (of meat)" .)