Clean six-footer having one month in charge (10)
I believe the answer is:
antiseptic
'clean' is the definition.
(associated in meaning)
'six-footer having one month in charge' is the wordplay.
'six footer' becomes 'ant' (an ant has six feet).
'having' means one lot of letters go next to another.
'one' becomes 'i' (Roman numeral).
'month' becomes 'sept' (Sept is an example).
'in charge' becomes 'ic' (abbreviation for 'in charge').
'ant'+'i'+'sept'+'ic'='ANTISEPTIC'
(Other definitions for antiseptic that I've seen before include "Clinical" , "Designed to counteract infection" , "Preventing growth of microorganisms" , "Preventing growth of, eg, bacteria" , "germicide" .)