In conclusion, the French play regularly on street (6)
I believe the answer is:
lastly
'in conclusion' is the definition.
(synonyms)
'the french play regularly on street' is the wordplay.
'the french' becomes 'la' ('the' in French).
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'on' means one lot of letters go next to another.
'street' becomes 'st' (abbreviation).
The alternate letters of 'play' are 'ly'.
'ly' put after 'st' is 'stly'.
'la'+'stly'='LASTLY'
(Other definitions for lastly that I've seen before include "In the end" , "In conclusion" , "Finally, to conclude with" .)