Enthralling European exploit for one stout yeoman (9)
I believe the answer is:
beefeater
'yeoman' is the definition.
('beefeater' can be a synonym of 'yeoman')
'enthralling european exploit for one stout' is the wordplay.
'enthralling' is an insertion indicator.
'european' becomes 'e' (abbreviation e.g. EU).
'exploit' becomes 'feat' ('feat' can be a synonym of 'exploit'**).
'for' means one lot of letters go next to another.
'one stout' becomes 'beer'.
'e'+'feat'='efeat'
'efeat' placed within 'beer' is 'BEEFEATER'.
(Other definitions for beefeater that I've seen before include "Yeoman warder of the Tower of London" , "Bodyguard of the British monarch" , "Yeoman of the Guard; carnivore" , "One might guard" , "royal bodyguard" .)