Strong Brussels youth raised in a medieval way (6)
I believe the answer is:
feudal
'in a medieval way' is the definition.
(resembling feudalism)
'strong brussels youth raised' is the wordplay.
'strong' becomes 'f' (musical symbol for 'forte', 'strong' in Italian).
'brussels' becomes 'EU' (European Parliament is based in Brussels).
'youth' becomes 'lad' (lad means a young man).
'raised' says the letters should be written in reverse (going up in a down clue).
'lad' back-to-front is 'dal'.
'f'+'eu'+'dal'='FEUDAL'
(Other definitions for feudal that I've seen before include "Reactionary" , "Pertaining to fiefs" , "Kind of system of holding land in Middle Ages" , "related to outdated system" , "Relating to land held on condition of service" .)