The most common and most likely answer to this crossword clue is the 6 plus 5 letter word QUARTZ CLOCK
Q
U
A
R
T
Z
C
L
O
C
K
Buddy explains!
The straight part
We know that "one indicating ‘Time!’" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one indicating ‘time!’ = quartz clock.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.