Plan to cover place in our mouldy cheese (9)
I believe the answer is:
mousetrap
'mouldy cheese' is the definition.
(cheese may be used to catch a mouse)
'plan to cover place in our' is the wordplay.
'plan' becomes 'map' (I've seen this before).
'to cover' is an insertion indicator.
'place' becomes 'set' (setting is a kind of placing).
'in' is an insertion indicator.
'set' put into 'our' is 'ousetr'.
'map' placed around 'ousetr' is 'MOUSETRAP'.
(Other definitions for mousetrap that I've seen before include "Poor-quality cheese" , "Rodent catcher" , "Snare for vermin" , "Cheese-baited snare" , "Poor cheese (colloq.)" .)