The most common and most likely answer to this crossword clue is the 5 letter word MATHS
M
A
T
H
S
More clues leading to the result MATHS
- Charlatan's about to cover start of tough subject
- With a degree, I leave this subject
- Covering extremely hazardous subject
- Turing practised it at home in the middle of Bloomsbury
- Mother faces this having dropped one school subject
- Scholar takes this after dropping one school subject
- Subject dull and hard — son comes last
- Science degree thus not needing university
- Its teaching can be applied
- Subject brought back by some of ticklish Tamils
Buddy explains!

The straight part
We know that "Subject" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case subject = maths.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 MATHS mean?
MATHS noun- An abstract representational system used in the study of numbers, shapes, structure, change and the relationships between these concepts.
- A person's ability to count, calculate, and use different systems of mathematics at differing levels.