Gas, across the pond (6)
I believe the answer is:
petrol
'gas across the pond' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for petrol that I've seen before include "Liquid fuel" , "Fuel for the internal combustion engine" , "The juice" , "Fuel for road vehicles" , "Mineral oil refined as fuel" .)