In Columbus he lacked a measure of corn (6)
I believe the answer is:
bushel
'measure of corn' is the definition.
'in columbus he lacked a' is the wordplay.
'in' indicates a hidden word.
'BUSHEL' is hidden in the letters of 'columbus he lacked a'.
(Other definitions for bushel that I've seen before include "Imperial measure of liquid or dry capacity" , "Old grain measure" , "A dry measure; may hide light" , "A few pecks wanted" , "Imperial measure for grain" .)