The most common and most likely answer to this crossword clue is the 7 letter word REGULAR
I've seen this crossword clue in Independent
R
E
G
U
L
A
R
More clues leading to the result REGULAR
- Controller loses to orderly
- Artillery regiment with gun elevated in routine
- Typical long-standing customer
- Professional soldier’s uniform
- Soldier in uniform, in 19
- Soldier returning artillery piece
- Frequent customer having predictable movements
- Soldier‘s uniform
- Pull over into a position behind according to established practice
- Send back something that might shoot a Republican soldier
Buddy explains!

The straight part
We know that "according to established practice" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case according to established practice = regular.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 REGULAR mean?
REGULAR noun- A member of the British Army (as opposed to a member of the Territorial Army or Reserve).
- A frequent, routine visitor to an establishment.
- A frequent customer, client or business partner.
- A coffee with one cream and one sugar.
- Anything that is normal or standard.
- A member of a religious order who has taken the three ordinary vows.
- A number for each year, giving, added to the concurrents, the number of the day of the week on which the Paschal full moon falls.
- A fixed number for each month serving to ascertain the day of the week, or the age of the moon, on the first day of any month.
- Bound by religious rule; belonging to a monastic or religious order (often as opposed to secular).
- Having a constant pattern; showing evenness of form or appearance.
- (of a polygon) Both equilateral and equiangular; having all sides of the same length, and all (corresponding) angles of the same size
- (of a polyhedron) Whose faces are all congruent regular polygons, equally inclined to each other.
- Demonstrating a consistent set of rules; showing order, evenness of operation or occurrence.
- Well-behaved, orderly; restrained (of a lifestyle etc.).
- Happening at constant (especially short) intervals.
- (grammar, of a verb, plural, etc) Following a set or common pattern; according to the normal rules of a given language.
- Having the expected characteristics or appearances; normal, ordinary, standard.
- Permanently organised; being part of a set professional body of troops.
- Having bowel movements or menstrual periods at constant intervals in the expected way.
- Exemplary; excellent example of; utter, downright.
- Having all the parts of the same kind alike in size and shape.
- Isometric.
- Riding with the left foot forward.
- (of a Borel measure) Such that every set in its domain is both outer regular and inner regular.
- Regularly, on a regular basis.