Mourn rate worked out for dividend (9)
I believe the answer is:
numerator
'dividend' is the definition.
(I know that numerator is a type of dividend)
'mourn rate worked out' is the wordplay.
'worked out' indicates an anagram.
'mourn'+'rate'='mournrate'
'mournrate' with letters rearranged gives 'NUMERATOR'.
'for' acts as a link.
(Other definitions for numerator that I've seen before include "Upper part of fraction" , "Top half of 1/2 , for example" , "quantity of parts?" , "Upper half of fraction" , "Figure going over a line" .)