Partnership has runs in it, that is plain (7)
I believe the answer is:
prairie
'plain' is the definition.
(type of plain)
'partnership has runs in it that is' is the wordplay.
'partnership has' becomes 'pair' (I can't explain this - if you can you should give a lot more credence to this answer).
'runs' becomes 'r' (cricket abbreviation).
'in it' is an insertion indicator.
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'pair' placed around 'r' is 'prair'.
'prair'+'ie'='PRAIRIE'
Can you help me to learn more?
(Other definitions for prairie that I've seen before include "Wide grassy plain" , "Open grassland of North America" , "Continental grassland of N America" , "Barren plain" , "Large treeless tract of grassland" .)