The most common and most likely answer to this crossword clue is the 5 letter word DREAD
I've seen this crossword clue in The Times
D
R
E
A
D
More clues leading to the result DREAD
- Fear about being caught by the old man
- Worry about troops governed by D-notice
- Anxiety about old man’s housing
- Fear uncoiling adder
- Terror of such locks?
- Man who has issue holding on to fear
- Fear old man’s about to be imprisoned
- Horror is not quite real when shown in 2-D
- Doctor first to dismiss initial fear
- Awesome Rastafarian
Buddy explains!

The straight part
We know that "Worry about" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case worry about = dread.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 DREAD mean?
DREAD noun- Great fear in view of impending evil; fearful apprehension of danger; anticipatory terror.
- Reverential or respectful fear; awe.
- Somebody or something dreaded.
- A person highly revered.
- Fury; dreadfulness.
- A Rastafarian.
- (chiefly in the plural) dreadlock
- To fear greatly.
- To anticipate with fear.
- To be in dread, or great fear.
- To style (the hair) into dreadlocks.
- Terrible; greatly feared.
- Awe-inspiring; held in fearful awe.