The most common and most likely answer to this crossword clue is the 6 plus 4 plus 5 letter word SILVER RING THING
I've seen this crossword clue in Financial Times
S
I
L
V
E
R
R
I
N
G
T
H
I
N
G
Buddy explains!
The straight part
We know that "Virgin’s undertaking" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case virgin’s undertaking = silver ring thing.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.