One starts a speech that another puts a stop to (9,4)

'one starts a speech that another puts a stop to' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.

'one starts a speech that another puts a stop to' is the wordplay.
I cannot really see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found in the answer.
'a' is present in the answer.
'to' is found in the answer.
This explanation may well be incorrect...

Can you help me to learn more?