The most common and most likely answer to this crossword clue is the 7 letter word LAMBERT
I've seen this crossword clue in Financial Times
L
A
M
B
E
R
T
More clues leading to the result LAMBERT
- Old English composer’s measure of brightness
- Quantity of light batter has to stay in the same condition, right?
- Subaltern carrying light warning Swiss polymath
- German scientist left warning light on top of transponder
- Officer receiving cautÂionary signal from light unit
- Young English king, with time, exhibits a measure of 3
- Composer left warning sign before end of street
Buddy explains!

The straight part
We know that "German scientist" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case german scientist = lambert.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 LAMBERT mean?
LAMBERT noun- A cgs unit of luminance; the brightness of a surface that emits one lumen per square centimetre