Union put up for instance with broadcast strike (8)
I believe the answer is:
marriage
'union' is the definition.
(synonyms)
'up for instance with broadcast strike' is the wordplay.
'up' says the letters should be written backwards (in down clue: letters go upwards).
'for instance' becomes 'eg' (synonyms).
'with' is a charade indicator (letters next to each other).
'broadcast' becomes 'air' (synonyms).
'strike' becomes 'ram' (I've seen this before).
'eg'+'air'+'ram'='egairram'
'egairram' reversed gives 'MARRIAGE'.
'put' is the link.
(Other definitions for marriage that I've seen before include "The nuptial ceremony" , "Formal union" , "'The - - of Figaro'" , "Wedding" , ""Till death do us part" arrangement" .)