Edges of double bed cut down to size (6)
I believe the answer is:
debunk
'cut down to size' is the definition.
(debunk can mean to discredit or expose)
'edges of double bed' is the wordplay.
'edges of' means to remove the middle letters.
'bed' becomes 'bunk' (bunk is a kind of bed).
'double' with its centre removed is 'de'.
'de'+'bunk'='DEBUNK'
(Other definitions for debunk that I've seen before include "Reveal as false, show up" , "Show to be exaggerated or false, claim or theory" , "Expose (pretentious claims?)" , "Expose false claims" , "Show to be falsely honoured" .)