The most common and most likely answer to this crossword clue is the 7 letter word SUNDIAL
I've seen this crossword clue in Financial Times
S
U
N
D
I
A
L
More clues leading to the result SUNDIAL
- On a fine day, time for reading here in the garden?
- Watch predecessor put students up
- Watch predecessor help students from east with Latin
- Daytime marker placed students in reverse order
- Island U-turn casts shadow for hours
- I land us in trouble getting something for the garden perhaps
- Times can be read on this — other paper put back
- Put a group of students up in an erection in the garden?
- One identifies the enemy casting a shadow
- Timepiece put back post-daylight
Buddy explains!

The straight part
We know that "Watch predecessor" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case watch predecessor = sundial.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 SUNDIAL mean?
SUNDIAL noun- A device measuring the time of day by the position of a shadow cast by a pole or plate (gnomon) upon an engraved series of marks.