Perhaps Boris Johnson welcomes special European (8)
I believe the answer is:
estonian
'european' is the definition.
(person from Estonia)
'perhaps boris johnson welcomes special' is the wordplay.
'perhaps boris johnson' becomes 'etonian' (Boris Johnson attended Eton College).
'welcomes' means one lot of letters goes inside another (in sense of 'invites in').
'special' becomes 's' (common abbreviation as in Special Air Service).
'etonian' placed around 's' is 'ESTONIAN'.
(Other definitions for estonian that I've seen before include "Foreign" , "Native of Tallinn, say" , "E. European" , "European language" , "Eastern Europe" .)