Taking object, servant I mistreated hides it (10)
I believe the answer is:
transitive
'taking object' is the definition.
(transitive verbs take a grammatical object)
'servant i mistreated hides it' is the wordplay.
'mistreated' is an anagram indicator.
'hides' is an insertion indicator.
'servant'+'i'='servanti'
'servanti' anagrammed gives 'transive'.
'transive' going around 'it' is 'TRANSITIVE'.
(Other definitions for transitive that I've seen before include "Passing over" , "Taking an object" .)