Hawaiian garland, but the French have one (3)
I believe the answer is:
lei
'hawaiian garland' is the definition.
(I've seen this in another clue)
'the french have one' is the wordplay.
'the french' becomes 'le' ('the' in French).
'have' means one lot of letters go next to another.
'one' becomes 'i' (Roman numeral).
'le'+'i'='LEI'
'but' acts as a link.
(Other definitions for lei that I've seen before include "Flower garland of Hawaii" , "Bloomers on line" , "Flower arrangements" , "Honolulu chain of flowers" , "Garland of flowers in Hawaii" .)