Demanding much in either effort or money (8)
I believe the answer is:
exacting
'demanding much' is the definition.
(I've seen this before)
'either effort or money' is the wordplay.
I cannot quite see how this works, but
'money' could be 'tin' (old-fashioned slang term for money) and 'tin' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'in' acts as a link.
Can you help me to learn more?
(Other definitions for exacting that I've seen before include "Making great demands like difficult task" , "Requiring great effort - sounds precise" , "Unreasonable in making demands" , "Difficult and onerous" , "Insisting upon" .)