He's a 'fiend' for physical fitness. [=he is very devoted to physical fitness]
She's been working 'like a fiend'. [=working very hard]
a dope/drug 'fiend' [='addict']
(..) I'll talk to Tom. That's all I was asking. We simply can't afford to allow the-- We got a guy who's almost perfect. He's a libertarian drug fiend - marinating in a mobile home. - Shh. I didn't agree with President Reagan on many things, but there was some merit (..)2013 TvShow: House of Cards Title: Chapter 2 Season: 1 Episode 2