The most common and most likely answer to this crossword clue is the 9 letter word REARGUARD
I've seen this crossword clue in The Times
R
E
A
R
G
U
A
R
D
More clues leading to the result REARGUARD
- Defence stern given by rail employee
- Defending month being taken up in Bishop engaging in study
- Nurture and protect tail enders
- Right muff of a military formation?
- Protection during withdrawal from a rare drug treatment
- Diehards bring up a drug, oddly
- A rare drug manufactured for ultimate fighters?
- Type of action soldiers might get in buttock-padded pants?
- Stern mind in conservative element
- Body of soldiers behind a drug bust
Buddy explains!

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 REARGUARD mean?
REARGUARD noun- The rearmost part of a force, especially a detachment of troops that protect the rear of a retreating force.
- The defence, collectively the defenders.