Use moral force if it justifies, in the end, the means (4)
I believe the answer is:
sway
'use moral force if it' is the definition.
I can't tell whether this defines the answer.
'justifies in the end the means' is the wordplay.
'in the end' indicates one should take the final letters.
'the means' becomes 'way' (a way or means of doing something).
The last letter of 'justifies' is 's'.
's'+'way'='SWAY'
Can you help me to learn more?
(Other definitions for sway that I've seen before include "Swing - lean - persuade" , "Influence; dominance" , "Rule; move to and fro" , "Vacillate" , "Oscillate" .)