Plainly apparent when lid lifted off secret (5)
I believe the answer is:
overt
'plainly apparent' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for overt that I've seen before include "totally visible" , "Openly displayed" , "Voter (anag.)" , "This is not hard to see" , "Done in an obvious way" .)