Plot many intended to be overheard (9)
I believe the answer is:
allotment
'plot' is the definition.
(I've seen this before)
'many intended to be overheard' is the wordplay.
'many' becomes 'allot' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'intended' becomes 'meant' (to mean something is to intend it).
'to be overheard' shows a homophone (sound like) (I've seen 'were overheard' mean this).
'meant' is a homophone of 'ment'.
'allot'+'ment'='ALLOTMENT'
Can you help me to learn more?
(Other definitions for allotment that I've seen before include "Where vegetables may be produced" , "Rented garden plot" , "Plot of land rented for growing vegetables" , "allocation" , "Piece of land let out for cultivation" .)