Say nothing, nothing, nothing. Just go away (4)
I believe the answer is:
shoo
'go away' is the definition.
(I've seen this before)
'say nothing nothing nothing' is the wordplay.
'say nothing' becomes 'sh' ('sh' is said to tell someone to say nothing).
'nothing' becomes 'O' (looks like zero - 0).
'nothing' becomes 'O' (looks like zero - 0).
'sh'+'o'+'o'='SHOO'
'just' is the link.
(Other definitions for shoo that I've seen before include "Get lost!" , "Word used to frighten away animals" , "Sling your hook!" , "word of dismissal" , "Dismissive remark" .)