As equipment in theatre idle sister wrecked (10)
I believe the answer is:
sterilised
'as equipment in theatre' is the definition.
(operating theatre)
'idle sister wrecked' is the wordplay.
'wrecked' indicates an anagram.
'idle'+'sister'='idlesister'
'idlesister' with letters rearranged gives 'STERILISED'.
(Other definitions for sterilised that I've seen before include "Like theatre equipment" , "immaculately clean" , "Thoroughly cleaned" .)