It means a lot (7)
'it' is the definition.
The definition suggests a singular noun which matches the answer.
'a lot' is the wordplay.
I cannot quite see how this works, but
'lot' could be 'ill' (ill is a kind of lot) and 'ill' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
'means' acts as a link.
Can you help me to learn more?
(Other definitions for million that I've seen before include "A power of 1 Down" , "Ten to the power of six" , "Large number" , "What mega means" , "1,000,000" .)