New postal centre in the field of agriculture (4)
I believe the answer is:
oats
'the field of agriculture' is the definition.
I can't judge whether this definition defines the answer.
'new postal centre' is the wordplay.
'new' indicates an anagram.
'centre' means to look at the middle letters.
The central letters of 'postal' are 'osta'.
'osta' with letters rearranged gives 'OATS'.
'in' is the link.
Can you help me to learn more?
(Other definitions for oats that I've seen before include "Seed grasses" , "Basis of porridge" , "Porridge ingredients" , "Young folk might sow wild ones" , "Hardy cereals eaten by horses" .)