The most common and most likely answer to this crossword clue is the 8 letter word VALUABLE
I've seen this crossword clue in The Daily Telegraph
V
A
L
U
A
B
L
E
More clues leading to the result VALUABLE
Buddy explains!

The straight part
We know that "Watch, perhaps" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case watch, perhaps = valuable.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 VALUABLE mean?
VALUABLE noun- A personal possession such as jewellery, of relatively great monetary value; — usually used in plural form.
- Having a great value.
- Estimable; deserving esteem.