Sausage variety, one almost identical to another, needed by Thursday (9)

'sausage variety' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'one almost identical to another needed by thursday' is the wordplay.
I cannot quite see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found in the answer.
'another' could be 'r' (I've seen this in other clues) and 'r' is located in the answer.
'thursday' could be 'th' (common abbreviation) and 'th' is located in the answer.
The remaining letters 'unger' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?