The most common and most likely answer to this crossword clue is the 12 letter word DEMONSTRATOR
I've seen this crossword clue in The Daily Telegraph
D
E
M
O
N
S
T
R
A
T
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More clues leading to the result DEMONSTRATOR
Buddy explains!
The straight part
We know that "See doomster rant terribly — that could be me" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case see doomster rant terribly — that could be me = demonstrator.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 DEMONSTRATOR mean?
DEMONSTRATOR noun- One who demonstrates anything, or proves beyond doubt.
- The forefinger.
- One who takes part in a demonstration; a protester.
- One who demonstrates products in a retail environment; a merchandiser.
- An item, particularly a vehicle, used in demonstrations to a customer or user.
- An assistant to a lecturer.
- One who teaches anatomy from the dissected parts.