Marriage makes a nice change after all (8)
I believe the answer is:
alliance
'marriage' is the definition.
(thesaurus)
'a nice change after all' is the wordplay.
'change' indicates anagramming the letters.
'after' means one lot of letters go next to another.
'a'+'nice'='anice'
'anice' anagrammed gives 'iance'.
'iance' put after 'all' is 'ALLIANCE'.
'makes' acts as a link.
(Other definitions for alliance that I've seen before include "Combination by treaty" , "Group acting together for common cause" , "A joining of forces" , "Bond" , "Wanting marriage" .)