Field sets off with half dropping out (3)
I believe the answer is:
lea
'field' is the definition.
(lea can mean a meadow or field of grass)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for lea that I've seen before include "pastoral setting" , "area of grassland" , "River flowing through London" , "Land growing grass" , "grazing area" .)