What does "traffic in position..." phrase mean? Recently heard the phrase "traffic in position..." issued by controller to one of the pilots, just wondering, what could it mean?
The phraseology in the question is incorrect.

If the planes on on the same runway without ASDE-X, the aircraft departing will be given:


  DELTA 2-7, RUNWAY 1, LINE UP AND WAIT, BOEING 7-2 6-MILE FINAL


The arriving aircraft will not be given a landing clearance until the holding aircraft has departed, but it will be told:


  AMERICAN 4-2-9, RUNWAY 1, CONTINUE, TRAFFIC HOLDING IN POSITION


If the planes are on different runways, it would be:


  DELTA 2-7, RUNWAY 1, LINE UP AND WAIT, TRAFFIC LANDING RUNWAY 19


and the other 


  AMERICAN 4-2-9, RUNWAY 1-9, CLEARED TO LAND, TRAFFIC HOLDING IN POSTION RUNWAY 1


Source: Air Traffic Conrollers Handbook, Section 3−9−4. LINE UP AND WAIT (LUAW)