Yep, Michael's got it as usual, this is the way to go. You'll need a regex (a Regular Expression - if you're not familiar with regex, a good tutorial is here: Regular Expression Tutorial - Learn How to Use Regular Expressions) to pull the tactic code out of your service name field - you want to use the "regular expression replace" option in the cloud connector.
I think this should work but you'll want to test it:
Regular expression to find: .*?T_(.*)$
Regular expression to replace: $1