Spike's within hearing (3)
I believe the answer is:
ear
'spike's' is the definition.
(spike is another term for an ear of grain)
'within hearing' is the wordplay.
'within' indicates a hidden word.
'EAR' is hidden within 'hearing'.
(Other definitions for ear that I've seen before include "Lend one and listen" , "Lug (colloq.)" , "Corn seed-holder" , "Seed container" , "Auditory organ" .)