Error message that triggers alarm? (4,4)
I believe the answer is:
tripwire
'triggers alarm?' is the definition.
The definition suggests a singular noun which matches the answer.
'error message' is the subsidiary indication.
'error' becomes 'trip' (trip is a kind of error).
'message' becomes 'wire' (wire is a kind of message**).
'trip'+'wire'='tripwire'
'that' is the link.
Can you help me to learn more?
(Other definitions for tripwire that I've seen before include "One setting off" , "that could trigger alarm" , "This may trigger alarm" , "Device working a trap or alarm when stumbled over" , "Trigger for booby trap" .)