Commentary on former place (10)
I believe the answer is:
exposition
'commentary' is the definition.
(I've seen this before)
'on former place' is the wordplay.
'on' means one lot of letters go next to another.
'former' becomes 'ex' (prefix meaning former or onetime).
'place' becomes 'position' (synonyms).
'ex' next to 'position' is 'EXPOSITION'.
(Other definitions for exposition that I've seen before include "fair" , "Public display" , "commentary" , "Account" , "large show" .)