Picture — of island — artist however inserted alongside identical one (8,3)

'picture' is the definition.
(Marathon Man is a 1976 film)

'island artist however inserted alongside identical one' is the wordplay.
I cannot really see how this works, but
'island' could be 'man' (the Isle of Man is an example) and 'man' is present in the answer.
'artist' could be 'ra' (Royal Academician, member of Royal Academy of Arts) and 'ra' is found within the answer.
'however' could be 'tho' (I've seen this in another clue) and 'tho' is located in the answer.
'one' could be 'an' (an apple is one apple) and 'an' is located in the answer.
A single letter 'm' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...

'of' acts as a link.