The most common and most likely answer to this crossword clue is the 6 letter word MINING
M
I
N
I
N
G
More clues leading to the result MINING
- Heavy industry I note during Chinese dynasty
- Digging up Chinese porcelain around home
- China arrests party member in office for underground activity
- Major industry like pottery, core doubled
- Underground activity fashionable during Chinese dynasty
- Dinky car, no good for fuel extraction, say
- Extractive industry‘s heartlessly making money
- Industry in which men are under-employed
- Digging for nickel in China perhaps
- Digging in, amid Chinese dynasty
Buddy explains!

The straight part
We know that "fuel extraction, say" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fuel extraction, say = mining.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does MINING mean?
MINING verb- To remove (ore) from the ground.
- To dig into, for ore or metal.
- To sow mines (the explosive devices) in (an area).
- To damage (a vehicle or ship) with a mine (an explosive device).
- To dig a tunnel or hole; to burrow in the earth.
- To dig away, or otherwise remove, the substratum or foundation of; to lay a mine under; to sap; to undermine.
- (by extension) To ruin or destroy by slow degrees or secret means.
- To pick one's nose.
- To earn new units of cryptocurrency by doing certain calculations.
- The activity of removing solid valuables from the earth.
- Any activity that extracts or undermines.
- The activity of placing explosives underground, rigged to explode
- Creation of new units of cryptocurrency by validating transactions and demonstrating proof-of-work