Old lady artist left to entertain relations of the husband (7)
I believe the answer is:
marital
'old lady artist left to entertain relations of the husband' is the definition.
I can't tell whether this defines the answer.
'old lady artist left to entertain relations' is the wordplay.
'old lady' becomes 'ma' (both can informally mean mother).
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'left' becomes 'l' (common abbreviation).
'to entertain' means one lot of letters goes inside another.
'relations' becomes 'it' (both can mean sex).
'ra'+'l'='ral'
'ral' placed around 'it' is 'rital'.
'ma'+'rital'='MARITAL'
Can you help me to learn more?
(Other definitions for marital that I've seen before include "Conjugal" , "to do with life together" , "Referring to a union" , "Ram tail (anag.)" , "describing matrimony" .)