Authentic tango on French street (4)
I believe the answer is:
true
'authentic' is the definition.
(I've seen this in another clue)
'tango on french street' is the wordplay.
'tango' becomes 'T' (phonetic alphabet: alpha, bravo, charlie etc.).
'on' is a charade indicator (letters next to each other).
'french street' becomes 'rue' (French for street or road).
't'+'rue'='TRUE'
(Other definitions for true that I've seen before include "Straight or correct" , "Consistent with fact" , "Unwavering" , "Real; loyal" , "Real or correct" .)