Pillow's center (3)
I believe the answer is:
els
'pillow's center' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for els that I've seen before include "Ernie - - (golfer)" , "Successful owner of several clubs" , "South African golfer" , "Golfer; elevated railways" , "US urban railways" .)