Mesh (3)
(Other definitions for fit that I've seen before include "Be the right size or shape" , "Strong" , "Healthy - episode of epilepsy" , "Certified OK by the doctor" , "Of a suitable standard" .)
'mesh' is the definition.
(I know that mesh can be written as net)
This is the entire clue.
(Other definitions for net that I've seen before include "Overall; mesh" , "Fish-catcher" , "Open-meshed fabric" , "Open mesh; catch" , "After expenses" .)