Still one sees legendary highlander (4)
I believe the answer is:
yeti
'legendary highlander' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe there's an association between them I don't understand?
'still one' is the wordplay.
'still' becomes 'yet' ('yet' can be a synonym of 'still').
'one' becomes 'i' (Roman numeral).
'yet'+'i'='YETI'
'sees' acts as a link.
Can you help me to learn more?
(Other definitions for yeti that I've seen before include "Anthropoid cryptid" , "doubts in its existence" , "creature never actually seen" , "Hairy recluse" , "something abominable" .)