Published five books on European defeat at the polls (7)
I believe the answer is:
outvote
'defeat at the polls' is the definition.
(I've seen this in another clue)
'published five books on european' is the wordplay.
'published' becomes 'out' (a published book is 'out').
'five' becomes 'V' (Roman numeral).
'books' becomes 'OT' (Old Testament).
'on' is a charade indicator (letters next to each other).
'european' becomes 'e' (abbreviation e.g. EU).
'out'+'v'+'ot'+'e'='OUTVOTE'
(Other definitions for outvote that I've seen before include "Defeat in election" , "Overrule by weight of opinion" .)