Network is back on, causing stress (7)
I believe the answer is:
tension
'stress' is the definition.
(I know that stress can be written as tension)
'network is back on' is the wordplay.
'network' becomes 'ten' (I am not sure about this - if you are sure you should believe this answer much more).
'back' shows that the letters should be reversed in order.
'is' backwards is 'si'.
'ten'+'si'+'on'='TENSION'
'causing' is the link.
Can you help me to learn more?
(Other definitions for tension that I've seen before include "anxious state" , "Stretched, uneasy, condition" , "State of strain or suspense" , "The effect of force exerted in or on something" , "Mental or emotional strain" .)