Perfectionist must see agreement is in Italian (8)
I believe the answer is:
idealist
'perfectionist' is the definition.
(I've seen this before)
'agreement is in italian' is the wordplay.
'agreement' becomes 'deal' (deal is a kind of agreement).
'in' means one lot of letters goes inside another.
'italian' becomes 'it' (abbreviation for Italian).
'deal'+'is'='dealis'
'dealis' going into 'it' is 'IDEALIST'.
'must see' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for idealist that I've seen before include "philosopher" , "Utopian" , "Detail is about person with aspirations toward perfection (8)" , "Person with high and unselfish standards" , "Details I accumulated about person with best intentions" .)