The most common and most likely answer to this crossword clue is the 7 letter word OUTWORK
O
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Buddy explains!
The straight part
We know that "Perform better than/another part of defence" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case perform better than/another part of defence = outwork.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 OUTWORK mean?
OUTWORK noun- A minor, subsidiary fortification built beyond the main limits of fortification.
- Agricultural work done outdoors in the fields.
- To work out to a finish; to complete.
- To work faster or harder than.