Take/draw somebody to one side
Definition 1 of 1
Pro Tip 1/3Private Conversation
Used when a sensitive or confidential topic needs to be discussed away from others. 
After the meeting, the manager took Sarah to one side to discuss her promotion.
Pro Tip 2/3Subtle Approach
Implies a gentle method to get someone's attention without causing embarrassment or drawing group attention. 
During the lunch break, I'll take him to one side to ask about his day.
Pro Tip 3/3Discretion
Emphasizes the need for tact or discretion in a situation, often to avoid making a scene. 
She took me to one side before explaining why my behavior was inappropriate.