The Spanish family initially left by artist in pose for his picture? (4-8)
I believe the answer is:
self-portrait
'his picture?' is the definition.
(a portrait of the artist)
'the spanish family initially left by artist in pose' is the wordplay.
I cannot quite understand how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found within the answer.
'left' could be 'l' (common abbreviation) and 'l' is located in the answer.
'artist' could be 'ra' (Royal Academician, member of Royal Academy of Arts) and 'ra' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'for' is the link.
(Other definitions for self-portrait that I've seen before include "Artist's own picture" , "Painting of the artist by the artist" , "Picture of its artist" .)