The most common and most likely answer to this crossword clue is the 7 letter word CRAZIER
I've seen this crossword clue in Financial Times
C
R
A
Z
I
E
R
Buddy explains!

The straight part
We know that "Extra: Barking" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case extra: barking = crazier.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 CRAZIER mean?
CRAZIER adjective- Flawed or damaged; unsound, liable to break apart; ramshackle.
- Sickly, frail; diseased.
- Of unsound mind; insane, demented.
- Out of control.
- Very excited or enthusiastic.
- In love; experiencing romantic feelings.
- Very unexpected; wildly surprising.