Some green and pleasant land (3)
I believe the answer is:
lea
'land' is the definition.
(I've seen this before)
'some green and pleasant' is the wordplay.
'some' says to take the centre.
'green' becomes 'ill' (eg looking green means looking ill).
'and' says to put letters next to each other.
'pleasant' becomes 'ea' (I can't explain this - if you can you should give a lot more credence to this answer).
The middle letter of 'ill' is 'l'.
'l'+'ea'='LEA'
Can you help me to learn more?
(Other definitions for lea that I've seen before include "''The lowing herd winds slowly o'er the ... '' (Gray)" , "Pasture, London river" , "River of east London" , "grazing area" , "Open pasture" .)