He's left inside writing material for institute in Europe (8)
I believe the answer is:
helsinki
'in europe' is the definition.
('Helsinki' is part of 'europe')
'he's left inside writing material for institute' is the wordplay.
'left' becomes 'l' (common abbreviation**).
'inside' is an insertion indicator.
'writing material' becomes 'ink' (I've seen this before).
'for' means one lot of letters go next to another.
'institute' becomes 'i' (common abbreviation as in MIT).
'hes' placed around 'l' is 'hels'.
'hels'+'ink'+'i'='HELSINKI'
(Other definitions for helsinki that I've seen before include "Finnish capital" , "port" , "Sikh line (anag)" , "Foreign city" , "Finland's capital" .)