Pepper money invested in sugar plant (7)
I believe the answer is:
cayenne
'pepper' is the definition.
(I know that cayenne is a type of pepper)
'money invested in sugar plant' is the wordplay.
'money' becomes 'yen' (Japanese currency).
'invested in' indicates putting letters inside.
'sugar plant' becomes 'cane' (I've seen this in another clue).
'yen' going inside 'cane' is 'CAYENNE'.
(Other definitions for cayenne that I've seen before include "Very hot, long peppers" , "Kind of pepper" , "Dried chilli powder" , "Hot red spice" , "Capital of French Guiana - river - pepper" .)