No good blocking state payment for computer security item (6)
I believe the answer is:
dongle
'computer security item' is the definition.
I don't know anything about this answer so I can't judge whether this works.
'no good blocking state payment' is the wordplay.
'no good' becomes 'ng' (abbreviation).
'blocking' means one lot of letters goes inside another (to block can mean to plug a gap in something).
'state payment' becomes 'dole' (dole can mean government benefits. I am not sure about the 'state' bit.).
'ng' put inside 'dole' is 'DONGLE'.
'for' is the link.
Can you help me to learn more?
(Other definitions for dongle that I've seen before include "Adapter used with a computer" , "computer accessory" , "Computer enabler" , "Golden (anag) - electronic device attached to a computer" .)