In this computerised world, will it not hold water? (3)
I believe the answer is:
net
'in this computerised world will it' is the definition.
The definition suggests a singular noun which matches the answer.
'not hold water?' is the wordplay.
'not' becomes 'n't' (synonyms).
'hold' indicates putting letters inside.
'water?' becomes 'e' (I can't justify this - if you can you should believe this answer much more).
'nt' placed around 'e' is 'NET'.
Can you help me to learn more?
(Other definitions for net that I've seen before include "Fish trap after deductions?" , "Final profit when all overheads have been deducted" , "land" , "Mesh or web" , "Tennis equipment" .)