18 possible answers to
Answers with 3 characters: MAR TAR Answers with 4 characters: BLUR SMUT SOIL SPOT Answers with 5 characters: SMEAR STAIN TAINT Answers with 6 characters: SCATHE BEFOUL DEFILE SMIRCH Answers with 7 characters: ASPERSE BESMEAR TARNISH Answers with 8 characters: BESMIRCH Answers with 9 characters: DENIGRATE