Cat beetled off before one's very eyes (10)
I believe the answer is:
'before one's very eyes' is the definition.
I can't judge whether this definition defines the answer.
'cat beetled off' is the wordplay.
'off' is an anagram indicator.
'catbeetled' with letters rearranged gives 'DETECTABLE'.
Can you help me to learn more?
(Another definition for detectable that I've seen is " apparent?".)