What are you doing, Socrates, half-drunk with weapon? (9)
I believe the answer is:
crossword
'what are you doing' is the definition.
(you are doing a crossword)
'socrates half-drunk with weapon?' is the wordplay.
'half' means to take half the letters.
'drunk' indicates anagramming the letters.
'with' is a charade indicator (letters next to each other).
'weapon?' becomes 'sword' (sword is a kind of weapon).
'socrates' halved is 'socr'.
'socr' is an anagram of 'cros'.
'cros'+'sword'='CROSSWORD'
(Other definitions for crossword that I've seen before include "One of these, first published December 1913 ..." , "that should make you think" , "See 8, 20 ac, 1, 15 dn" , "Puzzle with squares" , "this, appropriately" .)