Farewell notice that is universal (5)
I believe the answer is:
adieu
'farewell' is the definition.
(adieu is a kind of farewell)
'notice that is universal' is the wordplay.
'notice' becomes 'ad' (short for advert).
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'universal' becomes 'U' (film certificate).
'ad'+'ie'+'u'='ADIEU'
(Other definitions for adieu that I've seen before include "Parting word" , "the last word in France" , "Cheerio" , "All the best" , "Farewell, adios" .)