Middle pieces on the subject are in the wrong place (7)
I believe the answer is:
ectopic
'are in the wrong place' is the definition.
The answer and definition are different parts of speech. However, past participle verbs and adjectives occasionally define each other.
'middle pieces on the subject' is the wordplay.
'middle' says to take the centre.
'on' says to put letters next to each other.
'the subject' becomes 'topic' ('topic' can be a synonym of 'subject').
The central letters of 'pieces' are 'ec'.
'ec'+'topic'='ECTOPIC'
Can you help me to learn more?
(Other definitions for ectopic that I've seen before include "unusual pregnancy" , "out of place" , "In an unusual situation" , "In an abnormal position" .)