Mental health (6)
(Other definitions for morale that I've seen before include "Degree of optimism (of troops, perhaps)" , "Confidence, sense of wellbeing" , "Spirits" , "The spirit of a group or individual" , "Feeling of well-being" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">mental health</span>' is the definition.<br/ ><span class="explanation-format__explanation">(sanity is a kind of mental health)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for sanity that I've seen before include "State of having a healthy mind" , "Rational state" , "Mental normality" , "Rationality" , "Reason and coherence" .)