In Florida’s borders, strange site for a carnival (6)
I believe the answer is:
fiesta
'a carnival' is the definition.
(I've seen this before)
'in florida's borders strange site' is the wordplay.
'in' means one lot of letters goes inside another.
'borders' means to remove the middle letters (only the edge or border letters remain).
'strange' indicates anagramming the letters.
'florida' with its middle removed is 'fa'.
'site' is an anagram of 'iest'.
'fa' placed around 'iest' is 'FIESTA'.
'for' acts as a link.
(Other definitions for fiesta that I've seen before include "foreign holiday" , "Festivity, celebration" , "Festival, fete" , "public event abroad" , "Spanish holiday" .)