Semicircular canal count per ear (5)
I believe the answer is:
three
'semicircular canal count per ear' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for three that I've seen before include "Number of Furies or Norns" , "So many 12s today" , "Amount in a trio" , "Prime number" , "Trinity, triad" .)