The most common and most likely answer to this crossword clue is the 6 letter word VAINLY
I've seen this crossword clue in Financial Times
V
A
I
N
L
Y
Buddy explains!
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 VAINLY mean?
VAINLY adverb- In a vain pursuit; to no avail; She searched vainly for her reflection in the shattered mirror.
- With a vain attitude; in a self-approving manner; She stared vainly at her reflection in the mirror.