One makes a packet in one’s field (5)
I believe the answer is:
baler
'one' is the definition.
Both the answer and definition are singular nouns.
Perhaps they are linked in a way I don't understand?
I can't explain the rest of the clue.
(Other definitions for baler that I've seen before include "Farm machine" , "Hay-packing machine" , "Agricultural machine" , "Hay-bundling machine" , "Machine for bundling hay" .)