Part requiring European to be intense (6)
I believe the answer is:
severe
'be intense' is the definition.
(similar in meaning)
'part requiring european' is the wordplay.
'part' becomes 'sever' (severing is a kind of parting).
'requiring' says to put letters next to each other.
'european' becomes 'E' (abbreviation e.g. EU).
'sever'+'e'='SEVERE'
'to' acts as a link.
(Other definitions for severe that I've seen before include "Extreme - strict" , "Strict, hard" , "Unsparing and uncompromising" , "Formal - unsmiling" , "Harsh, rigorous" .)