About to ring apple-picker with incorrect wake-up call (8)
I believe the answer is:
reveille
'wake-up call' is the definition.
(I've seen this before)
'about to ring apple-picker with incorrect' is the wordplay.
'about' becomes 're' (regarding**).
'to ring' means one lot of letters goes inside another.
'apple picker' becomes 'eve' (in the Garden of Eden).
'with' means one lot of letters go next to another.
'incorrect' becomes 'ill'.
'eve'+'ill'='eveill'
're' enclosing 'eveill' is 'REVEILLE'.
(Other definitions for reveille that I've seen before include "Rousing bugle-call" , "Soldiers' wakening call" , "call to start" , "Morning call" , "Army waking signal" .)