The most common and most likely answer to this crossword clue is the 7 letter word REDOUBT
I've seen this crossword clue in The Times
R
E
D
O
U
B
T
More clues leading to the result REDOUBT
- Defence in question again
- Extra protection of information from computer discussed
- Have new concerns about defensive position
- Right to be uncertain about accepting ecologist’s earliest fieldwork
- Perhaps hesitate over something fortified
- Suspect for a second time in retreat
- Perhaps express suspicion over  fortress
- But it's a stronghold
- Soldiers suspect stronghold
- Brute aimlessly going around a party in the temporary fortification
Buddy explains!
The straight part
We know that "Defence" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case defence = redoubt.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 REDOUBT mean?
REDOUBT noun- A small, temporary, military fortification.
- A reinforced refuge; a fort.
- A place of safety or refuge.
- To fortify, to make into a stronghold.
- To dread.
- The return of doubt.
- To doubt again.