His pate seems to have a deficiency of hair, the villain! (6)
I believe the answer is:
pirate
This clue could be a double definition.
'his pate seems to have a deficiency of hair' is the first definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'villain' is the second definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'the' is the link.
Can you help me to learn more?
(Other definitions for pirate that I've seen before include "Silver, perhaps" , "Hook for one" , "Freebooter" , "Robber on the high seas" , "Teach, perhaps" .)