Enter a clue or pattern or both:
The Clue
Units of illumination (5 letter answer)
The Answer
PHOTS
Tags
Notes
The answer PHOTS is so rare that it appears less than once every 2500 puzzles.
Definition
PHOT as a noun:
1. a unit of illumination equal to 1 lumen per square centimeter; 10,000 phots equal 1 lux