In very casual speech, "sucker" can mean "thing". Here are some examples of things that you can call a "sucker":
- a fish that you're trying to catch
- a remote control that you're trying to find
- a steak that you're putting on the grill to cook
- your computer which recently broke
There's something lively-sounding about "sucker", so don't use it to talk about things which aren't doing anything interesting.