Walking here is conducting yourself and redeeming is to make wise use of. Both are used here with regard to how we spend our time in relation to the lost people around us, who are without the Lord Jesus Christ. Verse 6 in this same context shows that it is by speaking and answering that we perform this. In what way? Let your speech be seasoned with grace. Further light is shed on this in verse 3 where Paul requests prayer that he might be enabled to speak the mystery of Christ, God opening a door of utterance for him to do so.

So, we are exhorted to be wise in our conduct toward sinners. How? By making the most of the time given us. How? By speaking to and answering them. Regarding what? The mystery of Christ, and the grace of God as it is in Christ. God help me, in the place where He has opened a door for me to live and speak, to take this exhortation to heart, and act upon it. Oh, the continual struggle it is to keep my mind, heart, and all my efforts focused upon Christ and Him crucified. Oh, for the grace to determine with Paul, to know nothing else. I disobey the God Who opened the door for me, and greatly wrong those who hear me, if I deviate ever, at all.