Mark all dice differently (7)
I believe the answer is:
cedilla
'mark' is the definition.
(I know that cedilla is a type of diacritic)
'all dice differently' is the wordplay.
'differently' indicates anagramming the letters.
'all'+'dice'='alldice'
'alldice' anagrammed gives 'CEDILLA'.
(Other definitions for cedilla that I've seen before include "for French character" , "Mark indicating a softened consonant" , "Mark, in foreign language" , "The mark under the letter C in Spanish" , "Mark suggesting a 'c' should be pronounced an 's'" .)