Fool going round following the French language (5)
I believe the answer is:
latin
'language' is the definition.
(Latin is an example)
'fool going round following the french' is the wordplay.
'fool' becomes 'nit' (I've seen this before).
'going round' shows that the letters should be reversed in order.
'following' is a charade indicator (letters next to each other).
'the french' becomes 'la'.
'nit' back-to-front is 'tin'.
'tin' put after 'la' is 'LATIN'.
(Other definitions for latin that I've seen before include "Parent language of French,Romanian" , "and 15 Down: Student area of Paris" , "Language of Cicero" , "language class" , "The language of old Rome" .)