Cryptic crossword clue
At length, interrupting Earl and PM in a major way 7

The most common and most likely answer to this crossword clue is the 7 letter word GREATLY

I've seen this crossword clue in The Sunday Telegraph
G
R
E
A
T
L
Y

Buddy explains!

The straight part
We know that "in a major way" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case in a major way = greatly.
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 GREATLY mean?

GREATLY adverb
  1. To a great extent or degree.
  2. Nobly; magnanimously.

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