It’s responsible for a holdup online (7,3)
I believe the answer is:
clothes peg
'a holdup online' is the definition.
I can't tell whether this definition defines the answer.
'it's' is the wordplay.
I cannot really understand how this works, but
'it's' could be 'es' ('e' can mean 'electronic' which is similar to 'IT') and 'es' is located in the answer.
This explanation may well be incorrect...
'responsible for' is the link.
Can you help me to learn more?
(Other definitions for clothes peg that I've seen before include "one stuck on the line?" , "Fastener for washing line" , "Device to clip laundry to line" , "on-line clip?" .)