One who specified terms for stock manipulator lost six investors (10)
I believe the answer is:
stipulator
'one who specified terms for stock manipulator lost six investors' is the definition.
The definition suggests a singular noun which matches the answer.
'one who specified terms for stock manipulator lost' is the wordplay.
I cannot quite see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found within the answer.
'for' could be 'to' (eg both can mean 'in the opinion of') and 'to' is present in the answer.
'lost' could be 'l' (abbreviation in sporting league tables) and 'l' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?