The most common and most likely answer to this crossword clue is the 8 letter word SHADOWED
I've seen this crossword clue in The Daily Telegraph
S
H
A
D
O
W
E
D
More clues leading to the result SHADOWED
- Followed suit to begin with and was in debt
- Fish had debts tracked
- Dogged attitude defining leaders in broadcast
- Dogged son was in debt beforehand
- Eclipsed, soprano was once in debt
- Made gloomy commercial interrupting broadcast
- Fish due to be tracked covertly
- Followed in poor light
- Dogged son had had a debt
Buddy explains!

The straight part
We know that "tracked covertly" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case tracked covertly = shadowed.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 SHADOWED mean?
SHADOWED verb- To shade, cloud or darken.
- To block light or radio transmission from.
- To secretly or discreetly track or follow another, to keep under surveillance.
- To represent faintly and imperfectly.
- To hide; to conceal.
- To accompany (a professional) during the working day, so as to learn about an occupation one intends to take up.
- To make (an identifier, usually a variable) inaccessible by declaring another of the same name within the scope of the first.
- To apply the shadowing process to (the contents of ROM).