IIRC, a tactical officer is a security officer that specializes in shipboard weapons operation.
You began to see the formation of the security/tactical officer in the movies, as Checkov moved from the navigator's console to a special "weapons" console in TMP. In Star Trek III and VI, he appeared to have additional security duties, aside from his standard Weapons Officer posts (as well as being the acting-science officer in Spock's absence). By the time TNG rolled around, the security and tactical were part of the same profession.
Worf and Tasha were Chief Security Officers, but they were also the senior tactical officers (and manned tactical during crisis situations on the bridge).
If you check p.95 of the PG, you will find a "Tactical Officer" package for starting security officers. Security Officer professional skills (as stated on p. 73) include System Operation and Tactics, and two of the profession's abilities deal with tactical operations. So, yes, the Starship Security Officer Elite Profession covers tactical officers.
Davy Jones
"Frightened? My dear, you are looking at a man who has laughed in the face of death, sneered at doom, and chuckled at catastrophe! I was petrified."
-- The Wizard of Oz