It's excellent of the French to provide assistants (5)
'assistants' is the definition.
(aide is a kind of assistant)
'it's excellent of the french' is the wordplay.
'it's excellent' becomes 'ai'.
'of the french' becomes 'des'.
'to provide' acts as a link.
(Other definitions for aides that I've seen before include "Adjutants", "Helpers", "Ministerial assistants", "Helpful officers", "They help".)