Fishy, perhaps, it won't hold water (3)
I believe the answer is:
net
'it won't hold water' is the definition.
(I've seen this in another clue)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for net that I've seen before include "Overall; mesh" , "Catch, ensnare" , "Mesh for the bottom line?" , "Make" , "It's see-through" .)