"Cast a cold .../ On life, on death / Horseman, pass by" (gravestone of W B Yeats) (3)
I believe the answer is:
eye
(Other definitions for eye that I've seen before include "Location of 11dn" , "Centre of hurricane" , "Centre of storm" , "'Cast a cold ... on life, on death' (Yeats)" , "It accommodates a pupil" .)