Sweetener left upper-class politician with new rug and sofa (4,2,5)

'new rug and sofa' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'sweetener left upper-class politician' is the wordplay.
I cannot quite see how this works, but
'sweetener' could be 'sugar' (sugar is a kind of sweetener) and 'sugar' is present in the answer.
'left' could be 'l' (common abbreviation) and 'l' is located in the answer.
'politician' could be 'mp' (Member of Parliament) and 'mp' is located in the answer.
'upper-class' could be 'u' (similar in meaning) and 'u' is found in the answer.
The remaining letters 'of' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

'with' is the link.

Can you help me to learn more?