Unpleasant person – one going in all directions (5)
I believe the answer is:
swine
'unpleasant person' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'one going in all directions' is the wordplay.
'one' becomes 'i' (Roman numeral).
'going in' means one lot of letters goes inside another.
'all directions' becomes 'swne' (compass directions).
'i' going within 'swne' is 'SWINE'.
Can you help me to learn more?
(Other definitions for swine that I've seen before include "Nasty people" , "Pig, pigs" , "cad" , "Archaic pigs, Gadarene in Bible" , "Contemptible person; pigs" .)