The phrase "a chunk of what" is correct and usable in written English.
It can be used when referring to a portion or segment of something, often in a context where you are discussing parts of a larger whole.
Example: "In the meeting, we discussed a chunk of what we need to accomplish this quarter."
Alternatives: "a portion of what" or "a segment of what".
But then something solid struck the palate, introducing a wholly unexpected element — a chunk of what tasted like smoked eel.
The great park, he said, is "a chance to give people back a chunk of what they've lost".
Recipients also didn't tend to blow the money on booze or cigarettes, and many even invested a chunk of what they received.
This was then a key playground in the great game with the Russians, who had long occupied a chunk of what is now north-eastern Turkey.
I do not believe the Nicaraguan government is willing to give up a chunk of what they believe is their property".
That the Afghan project is on thin ice and that, collectively, the West was responsible for a chunk of what went wrong, though much of the rest the Afghans were responsible for.
More recently, he has focussed much of his time on the Imus Ranch, an eight-hundred-and-ten-acre cattle ranch that he launched with a gift of a million dollars, a considerable chunk of what is believed to be a seven-million-dollar salary.
As long as the startup remains steadfastly focussed on customer service and can provide a superior experience to competing online pharmacies, he thinks the company can take a decent chunk of what is a large market.
It is a small chunk of what was once a 15,000-ton mound of waste from Philadelphia.
She says that AWS has a big chunk of what essentially is a very small piece of the potential market, and she believes her company has plenty of time to catch up and grab a substantial share of the remainder.
In the Los Angeles Times, Doyle McManus writes: "Reducing [its] population would solve a big chunk of what has become an... insoluble problem.
