Gears do it (4)
I believe the answer is:
mesh
'gears do it' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for mesh that I've seen before include "Network fabric - engage with it" , "Engage; net" , "Interweave - netting" , "Undeviating" , "Net fabric" .)