Just not opening original text, leading to unease (6)
I believe the answer is:
qualms
'unease' is the definition.
(qualms are uneasy feelings)
'just not opening original text leading' is the wordplay.
'just' becomes 'equal' (just can mean equal or fair).
'not opening' means to remove the first letter (the opening letter is removed).
'original text' becomes 'MS' (abbreviation for manuscript).
'leading' is a charade indicator (letters next to each other).
'equal' with its first letter taken off is 'qual'.
'qual'+'ms'='QUALMS'
'to' acts as a link.
(Other definitions for qualms that I've seen before include "Misgivings, feelings of uneasiness" , "Misgivings, pangs of conscience" , "Feelings of doubt" .)