Altium Microstrip routing
Your best bet would be to create a new clearance rule (Design -> Rules -> right-click "Clearance" in the left pane, select "New Rule", open up the new rule you just created (it'll be titled "Clearance_X" where 'X' is the highest number you see) and in the section labeled "Where The First Object Matches", open the dropdown and select "Net". A new dropdown will appear, and you just need to select your RF Antenna net from the list. Then set the clearance in the "Constraints" section. This will apply this clearance rule to your RF antenna net only, and this will ensure that the polygon, components, and other traces are pulled back from this track. Keep in mind you will probably need to repour your polygon after setting the rule (Go to Tools -> Polygon Pours -> Repour All, or shortcut T-G-A).