Tall crop (4)
I believe the answer is:
corn
'tall crop' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for corn that I've seen before include "In song from 'Oklahoma' this is as high as an elephant's eye" , "Cereal grass" , "Grain - thick skin" , "Toe growth" , "Cereal; grain" .)