European went ahead, having shock treatment chosen (7)
I believe the answer is:
elected
'chosen' is the definition.
(electing is a kind of choosing)
'european went ahead having shock treatment' is the wordplay.
'european' becomes 'E' (abbreviation e.g. EU).
'went ahead' becomes 'led' (led the way).
'having' means one lot of letters goes inside another.
'shock treatment' becomes 'ECT' (ECT is an example).
'led' placed around 'ect' is 'lected'.
'e'+'lected'='ELECTED'
(Other definitions for elected that I've seen before include "Selected by a vote" , "Chosen by ballot" , "Voted into office" , "In a position" , "Chosen for office" .)