Spot Greek character around end of alphabet (6)
I believe the answer is:
stigma
'spot' is the definition.
(thesaurus)
'greek character around end of alphabet' is the wordplay.
'greek character' becomes 'sigma' (letter from the Greek alphabet**).
'around' means one lot of letters goes inside another.
'end of' suggests the final letters.
The final letter of 'alphabet' is 't'.
'sigma' going around 't' is 'STIGMA'.
(Other definitions for stigma that I've seen before include "Disgraceful sign" , "Blot" , "Mark of shame, stain on reputation" , "Badge of shame" , "Mark of infamy or disgrace" .)