Clarke, 27, joined the Iron on a three-month deal last Friday and scored on his debut as a substitute in the 1-1 draw with Sheffield United at the weekend.
"I don't think I have a future there," he told BBC Radio Humberside.
"The manager (Chris Powell) said when I went there that if I got in and played well then the shirt was mine to keep but I don't think I've had the opportunity."
He added: "I got a call from the manager on Thursday saying Scunthorpe were interested and I jumped at the chance.
"At any new club you want to hit the ground running and it breathed some confidence into me, which was nice.
"My match fitness isn't as high as I'd like it to be because I haven't played this season but hopefully I can train well and get in the team soon."
- Chris Powell