Concealed missing can-opener? Open! (5)
I believe the answer is:
overt
'open' is the definition.
(associated in meaning)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for overt that I've seen before include "Not concealed - public" , "Plain to see - manifest" , "Open and obvious" , "Open,up front" , "totally visible" .)