The most common and most likely answer to this crossword clue is the 6 letter word TICKER
T
I
C
K
E
R
More clues leading to the result TICKER
- Difficult problem? Learner's lost heart
- Watch recording: sort of reception
- Ever more stupid, husband lost heart
- Watch the heart
- Bloodsucker? The Speaker finally shows heart
- Show of hesitation after second heart
- Heart in aromatic kernel
- “Heart” label, not “head”
- Difficult problem? Student’s lost heart
- A kind of welcome cardiograph?
Buddy explains!

The straight part
We know that "Watch" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case watch = ticker.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 TICKER mean?
TICKER noun- One who makes a tick mark.
- A measuring or reporting device, particularly one which makes a ticking sound as the measured events occur.
- A ticker tape, either the traditional paper kind or a scrolling message on a screen.
- A heart, especially a human one.
- A birdwatcher who aims to see (and tick off on a list) as many bird species as possible.