Concerning girl, one on release (9)
I believe the answer is:
remission
'release' is the definition.
(remission is a kind of release)
'concerning girl one on' is the wordplay.
'concerning' becomes 're' (both can mean on a particular topic).
'girl' becomes 'miss' (term of address for an unmarried woman).
'one' becomes 'i' (Roman numeral).
're'+'miss'+'i'+'on'='REMISSION'
(Other definitions for remission that I've seen before include "Reprieve" , "improvement in patient's condition" , "lessening of pain" , "Forgiveness for sins for missioner" , "Lessening of a term of imprisonment" .)