Increasingly accepting nearly everyone’s state of mind (6)
I believe the answer is:
morale
'state of mind' is the definition.
(thesaurus)
'increasingly accepting nearly everyone's' is the wordplay.
'increasingly' becomes 'more'.
'accepting' indicates putting letters inside (inserted letters are accepted).
'nearly' means to remove the last letter.
'everyone' becomes 'all' (all people).
'all' with its last letter taken away is 'al'.
'more' placed around 'al' is 'MORALE'.
(Other definitions for morale that I've seen before include "Confidence, sense of wellbeing" , "Strength of purpose" , "Degree of optimism (of troops, perhaps)" , "State of mental confidence" , "Spirits" .)