Mark time during end of Greek holidays? (6)
I believe the answer is:
stigma
'mark' is the definition.
(I know that mark can be written as stigma)
'time during end of greek holidays?' is the wordplay.
'time' becomes 't' (abbreviation).
'during' is an insertion indicator.
'end of greek holidays?' becomes 'sigma' (Greek letter equivalent to the letter S).
't' going inside 'sigma' is 'STIGMA'.
(Other definitions for stigma that I've seen before include "Blot" , "Brand or mark of infamy" , "Symbol of disgrace or infamy" , "Mark of infamy or disgrace" , "Part of a flower" .)