The most common and most likely answer to this crossword clue is the 7 letter word TIERCET
T
I
E
R
C
E
T
More clues leading to the result TIERCET
Buddy explains!
The straight part
We know that "expressed in three lines" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case expressed in three lines = tiercet.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 TIERCET mean?
TIERCET noun- A triplet; three lines, or three lines rhyming together.