The most common and most likely answer to this crossword clue is the 9 letter word BOLOMETER
I've seen this crossword clue in The Times
B
O
L
O
M
E
T
E
R
Buddy explains!
The straight part
We know that "One records amounts of energy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one records amounts of energy = bolometer.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 BOLOMETER mean?
BOLOMETER noun- A sensitive device for detecting and measuring the energy of electromagnetic radiation.