(figuratively) to put one's finger on the problem, to put one's finger on it

(informal, figuratively) to conceal one's true feelings, to hide what one really thinks, not to reveal one's true convictions or allegiances

(figuratively) to be much mistaken, to bark up the wrong tree, to delude oneself, to need one's head examined, to have another think coming

to moderate one's impetuosity

(figuratively) to muck in, to put one's shoulder to the wheel, to get one's hands dirty

(informal) to get things straight, to make things perfectly clear, to put the record straight, to spell it out, to lay down the law

(transitive) to lay waste to, to wreak bloody havoc on

(figuratively, informal) to get one's hands dirty

Alternative form of mettre la clé sous la porte

to be dressed to the nines, to be dressed to kill