Eric prepared some grains (4)
I believe the answer is:
rice
'some grains' is the definition.
(I've seen this before)
'eric prepared' is the wordplay.
'prepared' is an anagram indicator.
'eric' is an anagram of 'RICE'.
(Other definitions for rice that I've seen before include "Grain from the paddy field" , "Cultivated food grass" , "Asian staple food" , "Cereal grass" , "Cereal grown in paddy fields" .)