Unquestioned supremacy not a condition to set the world alight? (13)

'unquestioned supremacy' is the definition.
'matchlessness' can be an answer for 'supremacy' (thesaurus). I am unsure of the 'unquestioned' bit.

'not a condition to set the world alight?' is the wordplay.
I cannot quite understand how this works, but
'not' could be 'less' (I've seen this in other clues) and 'less' is located in the answer.
'a' is found in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is located in the answer.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?