Ointment makes mark on light wood (6)
I believe the answer is:
balsam
'ointment' is the definition.
(balsam is a kind of ointment)
'mark on light wood' is the wordplay.
'mark' becomes 'm'.
'on' says to put letters next to each other.
'light wood' becomes 'balsa' (I've seen this before).
'm' put after 'balsa' is 'BALSAM'.
'makes' acts as a link.
(Other definitions for balsam that I've seen before include "Aromatic soothing medicament" , "Aromatic resin" , "Soothing ointment" , "Soothing herb" , "Fragrant medicinal gum from trees" .)