The 19-year-old Belgium international has been a revelation during his time at the Hawthorns, scoring 13 goals in 13 Premier League appearances, many coming as a substitute.
Clarke had previously hoped that Chelsea would sanction another loan move for Lukaku after affording him just one Premier League start in his debut season at Stamford Bridge, but he has now seemingly conceded defeat in his attempts to keep the youngster.
“He is Chelsea’s player. He belongs to Chelsea and he will go back there in the summer," Clarke told the Daily Mirror.
In the meantime, Clarke thanked Chelsea for allowing Lukaku the chance to impress at another club and work on reaching his potential after finding first-team opportunities initially hard to come by in England.
“I have never thought it would be possible Chelsea would let him come back next season," Clarke said. "He came on a season-long loan and we’re grateful we got him."