Can't sort out difference in tone (8)
I believe the answer is:
contrast
'difference in tone' is the definition.
'contrast' can be an answer for 'difference' (thesaurus). I'm not certain of the 'in tone' bit.
'can't sort out' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'cant'+'sort'='cantsort'
'cantsort' with letters rearranged gives 'CONTRAST'.
Can you help me to learn more?
(Other definitions for contrast that I've seen before include "Degree of difference in colour tones" , "Something completely different" , "Comparison to show differences" , "No tracts by way of difference" , "Degree of difference found on tracts" .)