have a thing

verb3

1. •
   (informal) To have a crush on, or a soft spot for, someone or something.

   • Brad has a thing for Mary.
   • I have a thing for ghost stories.
2. •
   (informal) To have an issue, such as a hang-up.

   • Don't ask Mary to drive you there, because she has a thing about highway driving. It sometimes gives her panic attacks.
   • He has a thing about not stepping on sidewalk cracks.
3. •
   (informal) To be in a casual or illicit romantic relationship.

   • Brad and Mary have a thing.
   • They’ve got a thing.