Went in formal wear then discarded half for date (9)
I believe the answer is:
twentieth
'date' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'went in formal wear then discarded half' is the wordplay.
'in' indicates putting letters inside.
'formal wear' becomes 'tie' (formal item of clothing).
'then discarded half' becomes 'th' (I am not sure about this - if you are sure you should believe this answer much more).
'went' placed into 'tie' is 'twentie'.
'twentie'+'th'='TWENTIETH'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for twentieth that I've seen before include "at the end of a score" , "Last century" , "Ordinal number for this century" .)