Once clothing removed, managing to treat disorder (6)
I believe the answer is:
angina
'disorder' is the definition.
(angina is a kind of disease)
'once clothing removed managing to treat' is the wordplay.
'once clothing removed' means to look at the middle letters.
'to treat' indicates anagramming the letters.
The middle of 'managing' is 'anagin'.
'anagin' is an anagram of 'ANGINA'.
(Other definitions for angina that I've seen before include "Painful heart complaint." , "Sudden cardiac pain" , "Painful heart condition" , "Pain from diseased heart" , "Cardiac complaint" .)