Curiously it’s a teen’s postprandial drink (8)
I believe the answer is:
anisette
'postprandial drink' is the definition.
(drink often taken after a meal, ie postprandially)
'curiously it's a teen's' is the wordplay.
'curiously' indicates anagramming the letters.
'its'+'a'+'teen'='itsateen'
'itsateen' is an anagram of 'ANISETTE'.
(Other definitions for anisette that I've seen before include "Liquorice flavoured liqueur" , "Liquorice-flavoured liqueur" , "Liqueur flavoured with seeds" , "Aromatic cordial drink" , "[APERITIF]" .)