With less American money invested, you get strength (9)
I believe the answer is:
lustiness
'strength' is the definition.
(lustiness is a kind of strength)
'with less american money invested you' is the wordplay.
I cannot really understand how this works, but
'american' could be 'us' (abbreviation for United States) and 'us' is found in the answer.
'money' could be 'tin' (I've seen this before) and 'tin' is located in the answer.
The remaining letters 'less' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'get' is the link.
Can you help me to learn more?
(Other definitions for lustiness that I've seen before include "virility" , "Vigour" .)