North American scientific establishment rejected church correspondence (7)
I believe the answer is:
balance
'correspondence' is the definition.
('balance' can be a synonym of 'correspondence')
'north american scientific establishment rejected church' is the wordplay.
'north american' becomes 'na'.
'scientific establishment' becomes 'lab' (I can't justify this - if you can you should give a lot more credence to this answer).
'rejected' says the letters should be written in reverse.
'church' becomes 'ce' (abbreviation for Church of England).
'na'+'lab'='nalab'
'nalab' in reverse letter order is 'balan'.
'balan'+'ce'='BALANCE'
Can you help me to learn more?
(Other definitions for balance that I've seen before include "emotional stability" , "Equilibrium or symmetry" , "It weighs - the remainder" , "Poise" , "Equilibrium or steady position" .)