Union notice that may be objected to (5)
I believe the answer is:
banns
'union notice' is the definition.
'banns' can be an answer for 'notice' (I have seen 'Notice of marriage ' mean 'banns' so perhaps 'notice' could also mean 'banns'). I am unsure of the 'union' bit.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for banns that I've seen before include "Notice of marriage read in church" , "Notices of marriage" , "Proclamation of intended marriage" , "Public announcement read in church of forthcoming marriage" , "Pre-wedding notice" .)