Sky Sports reports that an £8 million bid has gone in for the player.
Swansea's manager Graham Potter confirmed as much during a recent press conference.
Clucas started 29 league games for Swansea last season and would like to return to the Premier League.
But according to Sky, the two clubs are still far apart on his valuation.
It is unclear if a move could go through before the transfer window shuts for Premier League clubs.