Bland caper occurring around start of month (10)
I believe the answer is:
antiseptic
'bland' is the definition.
(antiseptic can mean bland or characterless)
'caper occurring around start of month' is the wordplay.
'caper' becomes 'antic' (synonyms).
'occurring around' indicates putting letters inside.
'start of month' becomes 'sept i' (resembles Sept 1).
'antic' going around 'septi' is 'ANTISEPTIC'.
(Other definitions for antiseptic that I've seen before include "Designed to counteract infection" , "Preventing growth of microorganisms" , "germicide" , "Preventing growth of, eg, bacteria" , "Clinical" .)