Hidden Wally often hit on pageboy, possibly during summit (8)
I believe the answer is:
trapdoor
'pageboy possibly during summit' is the definition.
I don't know anything about this answer so I can't judge whether this works.
'hidden wally often hit' is the wordplay.
I cannot quite understand how this works, but
'hit' could be 'rap' (rap can mean to hit or knock) and 'rap' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'on' acts as a link.
Can you help me to learn more?
(Other definitions for trapdoor that I've seen before include "Its movement can cause sudden drop" , "Horizontal access panel" , "stage opening?" , "from which Redgrave maybe escaped?" , "entrance into loft?" .)