Language the French can put together (5)
I believe the answer is:
latin
'language' is the definition.
(Latin is an example)
'the french can put together' is the wordplay.
'the french' becomes 'la'.
'can' becomes 'tin' ('tin' can be a synonym of 'can').
'put together' is a charade indicator (letters next to each other).
'la'+'tin'='LATIN'
(Other definitions for latin that I've seen before include "Parent language of French,Romanian" , "Language of old 8 down" , "Classical language" , "difficult subject" , "Language of the Caesars" .)