Require work by the sound of it (4)
I believe the answer is:
need
'require' is the definition.
(I know that require can be written as need)
'work by the sound of it' is the wordplay.
'work' becomes 'knead' (synonyms).
'by the sound of it' shows a homophone (sound like).
'knead' is a homophone of 'NEED'.
(Other definitions for need that I've seen before include "Want - poverty" , "Require; want" , "state requiring relief" , "'miss'" , "privation" .)