Notwithstanding that used in medical practice (6)
I believe the answer is:
method
'practice' is the definition.
(thesaurus)
'notwithstanding that used in medical' is the wordplay.
'notwithstanding that' becomes 'tho' (tho' is a poetic contraction of 'though').
'used in' indicates putting letters inside.
'medical' becomes 'med' (common abbreviation).
'tho' placed inside 'med' is 'METHOD'.
(Other definitions for method that I've seen before include "Style of technique, as of some actors" , "Orderly procedure, sometimes found in madness" , "rule" , "Manner, technique" , "Mode, procedure" .)