Disorder of some leeches (5)
I believe the answer is:
melee
'disorder' is the definition.
(thesaurus)
'of some leeches' is the wordplay.
'of' indicates a hidden word.
'MELEE' is hidden within 'some leeches'.
(Other definitions for melee that I've seen before include "Affray; muddled group" , "Scrap" , "Scrimmage" , "confused group" , "Confused fight or scuffle" .)