The most common and most likely answer to this crossword clue is the 7 plus 5 letter word DIGITAL WATCH
I've seen this crossword clue in Financial Times
D
I
G
I
T
A
L
W
A
T
C
H
More clues leading to the result DIGITAL WATCH
Buddy explains!

The straight part
We know that "timepiece" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case timepiece = digital watch.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.