Breach of law during French court case (10)
I believe the answer is:
infraction
'breach of law' is the definition.
(thesaurus)
'during french court case' is the wordplay.
'during' becomes 'in' (e.g. during February means in February).
'french' becomes 'fr' (abbreviation).
'court case' becomes 'action' (a legal action).
'in'+'fr'+'action'='INFRACTION'
(Other definitions for infraction that I've seen before include "transgression" , "Breach of agreement" , "Violation of law" .)