Clarke, 27, joined the Sky Blues on month-long loan deal on New Year's Day and has made two appearances, coming off the bench against Shrewsbury before starting the 3-0 FA Cup defeat at Tottenham on Saturday.
And, with 17-goal top scorer David McGoldrick having last week departed following the conclusion of his loan spell at the Ricoh Arena, Coventry have wasted little time in snapping up Clarke on a deal until 2015.
Manager Mark Robins said: "We knew it was going to be difficult to keep hold of David McGoldrick - and so it has proved - so we have acted quickly because we wanted to bring someone in that can score goals at this level and Leon can do that as he has proven.
"We need to fully integrate him into the squad as we've been doing over the last couple of games because he has shown, like he did against us this season, that he can give defences a torrid time and we believe he's the kind of player that can score a lot of goals for us."
The well-travelled frontman spent the first half of this season on loan at Scunthorpe, netting 11 goals in 15 appearances.