The main view of a picture? (8)
I believe the answer is:
seascape
'picture?' is the definition.
(I know that seascape is a type of picture)
'the main view' is the wordplay.
'the main' becomes 'sea' (the main is an old name for the sea).
'view' becomes 'scape' (I've seen this in another clue).
'sea'+'scape'='SEASCAPE'
'of a' is the link.
(Other definitions for seascape that I've seen before include "Marine view/picture" , "Oil" , "Painting - pea cases (anag)" , "View of ocean and sky" , "Main work" .)