Crossword Genius

Such fuel could appear a bit undervalued (6)

Ross

I believe the answer is:

diesel

I'm a little stuck... Click here to teach me more about this clue!

'such fuel' is the definition.
'diesel' can be an answer for 'fuel' (I've seen this before). I'm not sure about the 'such' bit.

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for diesel that I've seen before include "See lid, oddly, of the fuel" , "See lid for the engine" , "Rudolf __ , French-born German engine inventor, d.1913" , "Kind of engine" , "Lorry fuel" .)

I've seen this clue in the Evening Standard.
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