Leading hackers often use networked devices to harass (5)
I believe the answer is:
hound
'to harass' is the definition.
(I've seen this in another clue)
'leading hackers often use networked devices' is the wordplay.
'leading' says to take the initial letters (the leading letter of the word).
The first letters of 'hackers often use networked devices' is 'HOUND'.
(Other definitions for hound that I've seen before include "part of hunt" , "Pursue relentlessly" , "Pursue (like a dog?)" , "Hunting dog; harass" , "Sir Hugo's killer on Dartmoor" .)