One’s following plot that’s obscure (5)
I believe the answer is:
bedim
'that's obscure' is the definition.
(synonyms)
'one's following plot' is the wordplay.
'one's' becomes 'I'm' ('one is' is a formal way of saying 'I am').
'following' is a charade indicator (letters next to each other).
'plot' becomes 'bed' (a plot of land).
'im' put after 'bed' is 'BEDIM'.
(Other definitions for bedim that I've seen before include "Obscure" , "Make dark" .)