The most common and most likely answer to this crossword clue is the 8 letter word DIMINISH
I've seen this crossword clue in The Times
D
I
M
I
N
I
S
H
More clues leading to the result DIMINISH
- Drop off short skirt to be collected by fine-looking girl
- Drop baby into bowl
- Make less food, eating little
- Get smaller car in vessel
- Shrink in car probing attractive person
- Female style of Sixties attire facing quiet decline
- Make smaller container holding very little
- Shallow vessel containing little drop
- Drop off short skirt to be collected by stunner
- Belittle girl with short skirt? Say nothing!
Buddy explains!

The straight part
We know that "Drop off" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case drop off = diminish.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 DIMINISH mean?
DIMINISH verb- To make smaller.
- To become smaller.
- To lessen the authority or dignity of; to put down; to degrade; to abase; to weaken; to nerf (in gaming).
- To taper.
- To disappear gradually.
- To take away; to subtract.