Mercy makes one look big (7)
I believe the answer is:
quarter
'mercy' is the definition.
(I know that quarter is a type of mercy)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for quarter that I've seen before include "25 per cent" , "Fourth; part of town" , "Provide military accommodation" , "deadly action after draw?" , "Twenty-five cents" .)