Each pair of opposing sides produces a nobleman (4)
I believe the answer is:
earl
'a nobleman' is the definition.
(member of the nobility)
'each pair of opposing sides' is the wordplay.
I cannot quite understand how this works, but
'each' could be 'ea' (abbreviation) and 'ea' is found in the answer.
'sides' could be 'rl' (abbreviations for right and left) and 'rl' is found in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'produces' is the link.
Can you help me to learn more?
(Other definitions for earl that I've seen before include "Male member of British nobility" , "British nobleman" , "-- Grey, PM 1830-34" , "One who's been elevated" , "Countesss husband" .)