Tool which makes everything soundly (3)
I believe the answer is:
awl
'tool' is the definition.
(awl is a kind of tool)
'everything soundly' is the wordplay.
'everything' becomes 'all' (all things).
'soundly' shows a homophone (sound like).
'all' sounds like 'AWL'.
'which makes' acts as a link.
(Other definitions for awl that I've seen before include "Pointed tool for making small holes" , "a boring person may need?" , "Tool for piercing holes in leather" , "Boring tool sounds comprehensive" , "Hole-making tool" .)