Hesitant truce in an upheaval (9)
I believe the answer is:
uncertain
'hesitant' is the definition.
(thesaurus)
'truce in an upheaval' is the wordplay.
'upheaval' is an anagram indicator.
'truce'+'in'+'an'='truceinan'
'truceinan' anagrammed gives 'UNCERTAIN'.
(Other definitions for uncertain that I've seen before include "Changeable" , "Not definitely known" , "In doubt" , "Not definite" , "in the lap of the gods" .)