Tightrope walking was the act of walking along a rope that had been stretched until it had no slack.
In 2367, Jean-Luc Picard compared his acting as the Arbiter of Succession and a Starfleet officer to Worf's as a Klingon and a Starfleet officer, saying they both walked the same tightrope between two worlds (Starfleet and Qo'noS). (TNG: "Redemption")