In unity people finally sought redemption (9)
I believe the answer is:
atonement
'redemption' is the definition.
(I know that atonement is a type of redemption)
'in unity people finally sought' is the wordplay.
'in unity' becomes 'atone' (I can't justify this - if you can you should give a lot more credence to this answer).
'people' becomes 'men' (men are people).
'finally' says to take the final letters.
The final letter of 'sought' is 't'.
'atone'+'men'+'t'='ATONEMENT'
Can you help me to learn more?
(Other definitions for atonement that I've seen before include "Reparation (for a wrong)" , "'Penance, redemption (9)'" , "reparations?" , "satisfaction" , "Making amends" .)