The most common and most likely answer to this crossword clue is the 5 letter word TIMER
I've seen this crossword clue in The Sunday Telegraph
T
I
M
E
R
More clues leading to the result TIMER
- Watch, maybe, to send back
- Watch maybe as millions lodged in bank
- Watch, say, construction of mitre
- Watch to send back
- Row about one starting marathon clock
- Watch, say, brief spins
- Perhaps watch sphere rising
- One could show minutes into game, right?
- Grandfather may be an old one
- All letters redirected, watch post
Buddy explains!

The straight part
We know that "post" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case post = timer.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 TIMER mean?
TIMER noun- Someone or something which times.
- A device used to measure amounts of time.
- Any electronic function that causes a device to be able to do something automatically after a preset amount of time.