Somewhat nouveau – that includes Iris (4)
I believe the answer is:
uvea
'iris' is the definition.
(I've seen this before)
'somewhat nouveau that' is the wordplay.
'somewhat' says the answer is hidden in the clue.
'UVEA' is hidden within 'nouveau that'.
'includes' acts as a link.
(Other definitions for uvea that I've seen before include "bit of a looker" , "Pigmented part of eye" , "Iris's part" , "part of eye be seen" , "bit of mince pie!" .)