The most common and most likely answer to this crossword clue is the 8 letter word ROENTGEN
I've seen this crossword clue in The Guardian
R
O
E
N
T
G
E
N
More clues leading to the result ROENTGEN
- Measure of radiation, not energy almost entirely kinetic?
- X-ray unit or back specialist hospital department’s information
- Payment’s received over info for physicist
- Green ton? Wrong scientific unit!
- X-ray unit processes not green
- Let outside old information unit
- Endless energy not unusual for physicist
- X-ray unit
- New idea ______ had for degeneration?
- Right tone perhaps, to suppress information on scale of radiation
Buddy explains!

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 ROENTGEN mean?
ROENTGEN noun- A unit of exposure to ionizing radiation