Board member formerly with European Commission (4)
I believe the answer is:
exec
'board member' is the definition.
(I've seen this before)
'formerly with european commission' is the wordplay.
'formerly' becomes 'ex' (prefix meaning former or onetime).
'with' is a charade indicator (letters next to each other).
'european commission' becomes 'EC' (abbreviation).
'ex'+'ec'='EXEC'
(Other definitions for exec that I've seen before include "high-flier" , "CEO?" , "Board member" , "Senior businessperson (abbr)" , "Business manager (abbrev.)" .)