New duet has British premiere (5)
I believe the answer is:
debut
'premiere' is the definition.
(I've seen this in another clue)
'new duet has british' is the wordplay.
'new' is an anagram indicator.
'has' means one lot of letters goes inside another.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'duet' anagrammed gives 'deut'.
'deut' going around 'b' is 'DEBUT'.
(Other definitions for debut that I've seen before include "Tubed (anag.)" , "Aurora" , "First attempt" , "First appearance in society" , "Introduction" .)