Royal racket at first in bistro (5)
I believe the answer is:
diner
'bistro' is the definition.
(thesaurus)
'royal racket at first' is the wordplay.
'royal' becomes 'er' (I've seen this in other clues).
'racket' becomes 'din' (I've seen this before).
'at first' says to put letters next to each other.
'er' put after 'din' is 'DINER'.
'in' is the link.
(Other definitions for diner that I've seen before include "(Person eating in) restaurant" , "American cafe" , "Eater" , "one taking several courses" , "(One using) restaurant car" .)