Sinister trail pursued by Yankee (7)
I believe the answer is:
shadowy
'sinister' is the definition.
Both the definition and answer are adjectives. Perhaps you can see an association between them that I don't see?
'trail pursued by yankee' is the wordplay.
'trail' becomes 'shadow' (I've seen this before).
'pursued by' is a charade indicator (letters next to each other).
'yankee' becomes 'Y' (phonetic alphabet: alpha, bravo, charlie etc.).
'shadow'+'y'='SHADOWY'
Can you help me to learn more?
(Other definitions for shadowy that I've seen before include "hazy" , "Mysterious" , "Obscure, dark" , "Insubstantial" , "Obscure; dim" .)