Patriotic song of Frenchman, 'The Marseillaise' (6)
I believe the answer is:
anthem
'patriotic song' is the definition.
(I've seen this before)
'of frenchman the marseillaise' is the wordplay.
'of' indicates the answer is hidden within the clue.
'ANTHEM' is hidden within 'frenchman the marseillaise'.
(Other definitions for anthem that I've seen before include "The man for a popular song" , "National or church song" , "One for doomed youth" , "Uplifting song -- the man (anag)" , "air of patriotism?" .)