Dangle is a term used in intelligence

Intelligence (information gathering)

Intelligence assessment is the development of forecasts of behaviour or recommended courses of action to the leadership of an organization, based on a wide range of available information sources both overt and covert. Assessments are developed in response to requirements declared by the leadership...

 work to refer to an agent

Espionage

Espionage or spying involves an individual obtaining information that is considered secret or confidential without the permission of the holder of the information. Espionage is inherently clandestine, lest the legitimate holder of the information change plans or take other countermeasures once it...

 of one intelligence agency or group who pretends to be interested in defecting or turning to another intelligence agency or group.

The goal of a dangle is to convince the second or foreign intelligence agency that they have changed loyalties by offering to act as a double agent

Double agent

A double agent, commonly abbreviated referral of double secret agent, is a counterintelligence term used to designate an employee of a secret service or organization, whose primary aim is to spy on the target organization, but who in fact is a member of that same target organization oneself. They...

. The dangle then feeds information to their original agency and/or gives disinformation to the second or foreign intelligence agency.