Goes without, sounding careless (5)
I believe the answer is:
lacks
'goes without' is the definition.
(to lack is to be missing or go without)
'sounding careless' is the wordplay.
'sounding' shows a homophone (sound like).
'careless' becomes 'lax' (synonyms).
'lax' sounds like 'LACKS'.
(Other definitions for lacks that I've seen before include "Needs" , "Doesn't have" , "Wants, is deficient in" , "Is without, wants" , "Has a want" .)