Helping someone out for a period of time. Also visible in the One Direction song with the same name, written by Niall Horan. As "No Control" it's one of the more mature/edgy songs the band has written and performed. The meaning of "Temporary Fix" shows in the lyrics.
"You can call me, when you're lonely. When you can't sleep, I'll be your Temporary Fix. You control me, even if it's just tonight."