The most common and most likely answer to this crossword clue is the 7 letter word REGIMEN
I've seen this crossword clue in The Times
R
E
G
I
M
E
N
More clues leading to the result REGIMEN
- Most of army unit's recommended diet
- Battalion having no time for course of therapy
- Troops short of time prescribed treatment
- Plan made by soldier among other soldiers
- Body temperature deficient? Course of therapy needed
- Impressing me, country reversed rule
- Engineers and soldiers following soldier’s rules
- Army group having no time for slimming course
- . Emigré upset by new government
- Diet has military group shedding tons
Buddy explains!

The straight part
We know that "rule" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rule = regimen.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 REGIMEN mean?
REGIMEN noun- Orderly government; system of order; administration.
- Any regulation or remedy which is intended to produce beneficial effects by gradual operation.
- (grammar) object
- (grammar) A syntactical relation between words, as when one depends on another and is regulated by it in respect to case or mood; government.
- Diet; limitations on the food that one eats, for health reasons.