A lot of grind - that could be positive or negative (7)
I believe the answer is:
million
'a lot of grind that could be positive or negative' is the definition.
The definition and answer can be both quantities as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'a lot of grind that could be' is the wordplay.
'a lot of' means to remove the last letter (a lot of the word but not all of it).
'grind' becomes 'mill' (synonyms).
'that could be' becomes 'lion' (I can't justify this - if you can you should believe this answer much more).
'mill' with its last letter removed is 'mil'.
'mil'+'lion'='MILLION'
Can you help me to learn more?
(Other definitions for million that I've seen before include "Ten thousand hundreds" , "Ten to the power of six" , "A thousand thousnad" , "A power of 1 Down" , "One followed by six zeros" .)