The midfielder has been linked with a move to Fiorentina and has a year remaining on his current deal at the Hawthorns
The midfielder was an influential figure in West Brom's campaign last season as the club secured an eighth-placed finish in the Premier League.
Fiorentina have been linked with a move for the 26-year-old, who has a year remaining on his current deal, but Clarke believes it is imperative that the DR Congo international stays at West Brom.
"Youssouf has been excellent for us since I have been here and is one of the players we want to keep," said Clarke.
"I think come the summer the ones that we have to keep - that I want to keep - will still be at the club."