Mistake? Hope, perhaps, to conceal nothing (4)
I believe the answer is:
boob
'mistake?' is the definition.
(I've seen this before)
'hope perhaps to conceal nothing' is the wordplay.
'hope perhaps' becomes 'bob' (comedian Bob Hope. I am not sure about the 'perhaps' bit.).
'to conceal' indicates putting letters inside.
'nothing' becomes 'O' (looks like zero - 0).
'bob' enclosing 'o' is 'BOOB'.
Can you help me to learn more?
(Other definitions for boob that I've seen before include "Error" , "Embarrassing mistake" , "Mistake; breast (sl.)" , "Slip" , "Blunder (colloq.)" .)