Now one sees legendary creature (4)
I believe the answer is:
yeti
'legendary creature' is the definition.
(yeti is a kind of legendary creature)
'now one' is the wordplay.
'now' becomes 'yet' (I've seen this in another clue).
'one' becomes 'i' (Roman numeral).
'yet'+'i'='YETI'
'sees' acts as a link.
(Other definitions for yeti that I've seen before include "imaginary beast?" , "It probably doesn't exist" , "Himalayan mystery" , "Tibetan creature" , "An abominable animal!" .)