The most common and most likely answer to this crossword clue is the 11 letter word TRENDSETTER
I've seen this crossword clue in The Daily Telegraph
T
R
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N
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T
T
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R
More clues leading to the result TRENDSETTER
- One leading the way in drift with dog
- Nurse keeps Rex, the dog, for arbiter of taste
- Nurse keeps Rex and me, an avant-gardist
- Dog having to t-tear away in the lead, one ahead of the pack?
- Innovator initially tests revolutionary design on dog
- Time restrictions initially stop me for instance becoming a fashion icon
- One initiating rage?
- One leading the way in movement — crossword compiler
- Maybe Westwood runs in to take care of me
- Groundbreaker needs direction — street disrupted
Buddy explains!

The straight part
We know that "One initiating rage" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one initiating rage = trendsetter.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 TRENDSETTER mean?
TRENDSETTER noun- Someone who starts a trend, or makes one more popular