Sensitivity (10)
'sensitivity' is the definition.
(being tactful is being sensitive)
This is all the clue.
(Other definitions for tact that I've seen before include "Delicacy of feeling, skill in saying the right thing" , "measure of diplomacy?" , "Sensitivity, diplomacy" , "Skill in dealing with people" , "Consideration in dealing with others" .)
'sensitivity' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for tenderness that I've seen before include "Gentleness, sensitivity" , "sore?" , "Compassion" , "Gentle quality" , "Heart" .)