Begin with the French alarm (7)
I believe the answer is:
startle
'alarm' is the definition.
(I've seen this before)
'begin with the french' is the wordplay.
'begin' becomes 'start' ('start' can be a synonym of 'begin').
'with' means one lot of letters go next to another.
'the french' becomes 'le'.
'start'+'le'='STARTLE'
(Other definitions for startle that I've seen before include "Cause to jump" , "Take unawares with rattles" , "Alarm (someone)" , "Take by surprise" , "Scare" .)