Hex on hound's handsome tail (5)
I believe the answer is:
curse
'hex' is the definition.
(I know that hex can be written as curse)
'on hound's handsome tail' is the wordplay.
'on' is a charade indicator (letters next to each other).
'hound' becomes 'cur' (I've seen this in another clue).
'handsome tail' becomes 'se' (I am not sure about this - if you are sure you should believe this answer much more).
'cur' put next to 'se' is 'CURSE'.
Can you help me to learn more?
(Other definitions for curse that I've seen before include "Trouble" , "Malediction or expletive" , "Imprecate" , "Cause of harm or misery" , "Imprecation or oath" .)