Worry greatly about not perhaps reading perfectly (4)
I believe the answer is:
dead
'perfectly' is the definition.
(synonyms)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for dead that I've seen before include "Defunct" , "Not quick" , "Late; exact" , "Exhausted -- layabout" , "No longer alive" .)