Commercial that is for all to see, and so long (5)
I believe the answer is:
adieu
'so long' is the definition.
('adieu' can be a synonym of 'so long')
'commercial that is for all to see' is the wordplay.
'commercial' becomes 'ad'.
'that is' becomes 'ie' ('i.e.' can be a synonym of 'that is').
'for all to see' becomes 'u' (universal dvd certificate).
'ad'+'ie'+'u'='ADIEU'
'and' is the link.
(Other definitions for adieu that I've seen before include "Goodbye, madame" , "Farewell, Monsieur!" , "Gallic goodbye" , "A valediction" , "Farewell (French)" .)