The most common and most likely answer to this crossword clue is the 6 letter word OPENED
I've seen this crossword clue in Financial Times
O
P
E
N
E
D
More clues leading to the result OPENED
- Dictionary covering writer unwrapped
- Didn't shut reference book writer has gone into
- Started to write in reference book
- Began to write in reference book
- Writer must’ve done it to dictionary!
- Exposed valley with river running north
- Began to write in dictionary
- Started to write in dictionary, initially
- Began to write in wordbook
- Unwrapped a dictionary for writer to go through
Buddy explains!

The straight part
We know that "Writer must’ve done it to dictionary!" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case writer must’ve done it to dictionary! = opened.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 OPENED mean?
OPENED verb- To make something accessible or allow for passage by moving from a shut position.
- To make (an open space, etc.) by clearing away an obstacle or obstacles, in order to allow for passage, access, or visibility.
- To bring up, broach.
- To enter upon, begin.
- To spread; to expand into an open or loose position.
- To make accessible to customers or clients.
- To start (a campaign).
- To become open.
- To begin conducting business.
- To begin a side's innings as one of the first two batsmen.
- To bet before any other player has in a particular betting round in a game of poker.
- To reveal one's hand.
- (of a file, document, etc.) To load into memory for viewing or editing.
- To disclose; to reveal; to interpret; to explain.