As most petrol is now in Deal? (4-4)
I believe the answer is:
lead-free
'deal?' is the definition.
Both the definition and answer are adjectives. Perhaps they are linked in a way I don't understand?
'as most petrol is now' is the wordplay.
I cannot really see how this works, but
'now' could be 'ad' (AD, Anno Domini, as opposed to BC, Before Christ) and 'ad' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
'in' acts as a link.
Can you help me to learn more?
(Another definition for lead-free that I've seen is " Like most petrol".)