Hi,

we prefer to implement the removal procedures directly in the AV instead of create a tool for every malware.

Trojan Horse is just a family of malwares. Too generic to provide a specific removal procedure.

There are three possible scenarios:
1) SEP already detects this Trojan Horse then, open the risk logs, take the exact name of the virus and search it in our website. There you will find the proper removal procedure. In most of the situation it is enough to disable the System Restore and run a full scan in safe mode. This is the best removal tool.
2) You know that your machine are infected (for example thanks to another AV software) but SEP does not detect and remove it, in this case you have to submit the malware sample to Symantec in order to release the proper definitions
3) The malware is detected but not properly removed: open a case with the Technical Support or submit a sample to improve the quality of the detection and the removal of some malware variants

Cheers