The couple leveled with each other (6)
I believe the answer is:
evened
'other' is the definition.
The answer and definition are not the same part of speech. However, adjectives and past participle verbs occasionally define each other.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for evened that I've seen before include "Levelled" , "Made smooth and regular" , "Made level" , "Made smooth or equalised" .)