English reformer throttling leading European's neck (10)
I believe the answer is:
effrontery
'neck' is the definition.
'english reformer throttling leading european's' is the wordplay.
'english' becomes 'e' (abbreviation).
'reformer' becomes 'fry' (Elizabeth Fry).
'throttling' is an insertion indicator.
'leading' becomes 'front' (**).
'european' becomes 'e' (abbreviation e.g. EU).
'front'+'e'='fronte'
'fry' going around 'fronte' is 'ffrontery'.
'e'+'ffrontery'='EFFRONTERY'
(Other definitions for effrontery that I've seen before include "Impertinence" , "Audacity" , "Presumptuousness" , "Impudence" , "Gall" .)