Even so, setter is creature seldom seen (4)
I believe the answer is:
yeti
'creature seldom seen' is the definition.
'even so setter' is the wordplay.
'even so' becomes 'yet' (I've seen this in another clue).
'setter' becomes 'I' (the person that set the crossword).
'yet'+'i'='YETI'
'is' is the link.
(Other definitions for yeti that I've seen before include "fictional creature" , "mythical creature" , "Mythical Tibetan beast" , "A sort not reliably recorded" , "Tibetan creature" .)