The most common and most likely answer to this crossword clue is the 7 letter word GILBERT
I've seen this crossword clue in The Guardian
G
I
L
B
E
R
T
More clues leading to the result GILBERT
- Soldier beginning to leave guy’s unit for force
- Mr White‘s gerbil smeared over Tarantino’s head?
- William, say, born before Elizabeth, having gold-coloured clothing
- Librettist making three times as much in recession
- Lyricist, good one, boy singer mostly picked up
- Humorous writer, awkward blighter, hard to shake off
- Lyricist Pound swallowed by wild tiger
Buddy explains!
The straight part
We know that "Librettist" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case librettist = gilbert.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.