PIN providing on-line security? (7,3)
I believe the answer is:
clothes peg
'pin providing on-line security?' is the definition.
I can't tell whether this defines the answer.
'pin providing on' is the wordplay.
'pin' becomes 'peg' (synonyms).
'providing' becomes 'clothes' (I can't justify this - if you can you should give a lot more credence to this answer).
'on' says to put letters next to each other.
'peg' after 'clothes' is 'CLOTHES-PEG'.
(Other definitions for clothes peg that I've seen before include "Fastener for washing line" , "Device to clip laundry to line" , "one stuck on the line?" , "on-line clip?" .)