Even I find this creature fantastic (4)
I believe the answer is:
yeti
'this creature fantastic' is the definition.
(a legendary or fantastic creature)
'even i' is the wordplay.
'even' becomes 'yet' (synonyms).
'yet'+'i'='YETI'
'find' is the link.
(Other definitions for yeti that I've seen before include "Your claim to have seen one wouldn't be believed" , "Mysterious Himalayan creature" , "Tibetan creature" , "Himalayan wild man" , "Creature perhaps" .)