Undisciplined, goes without speaking (3)
I believe the answer is:
lax
'undisciplined' is the definition.
(I've seen this in another clue)
'goes without speaking' is the wordplay.
'goes without' becomes 'lacks' (to lack is to be missing or go without).
'speaking' indicates a 'sounds like' (homophone) clue.
'lacks' is a homophone of 'LAX'.
(Other definitions for lax that I've seen before include "Not strict or conscientious" , "Not sufficiently strict" , "without tension" , "Remiss" , "Slipshod" .)