Shockingly, it went with the last century (9)
I believe the answer is:
twentieth
'last century' is the definition.
(I've seen this before)
'shockingly it went with the' is the wordplay.
'shockingly' is an anagram indicator.
'with' is a charade indicator (letters next to each other).
'it'+'went'='itwent'
'itwent' after 'the' is 'theitwent'.
'theitwent' is an anagram of 'TWENTIETH'.
(Other definitions for twentieth that I've seen before include "Ordinal number for this century" , "at the end of a score" , "Last century" .)