Trojan.Agent refers to a generic Trojan malware detection. It is used for detections that are either associated with no specific malware families or not enough information is available to pinpoint the malware family.
This is the generic detection for traces of infection that can’t be attributed by a specific Trojan. Most of the time, these are harmless by themselves, but they are a sign of system infection. The traces could be leftovers from an already removed malware.
Malwarebytes can remove these traces without further user interaction.