Concert not now recalled, involving contralto and I (7)
I believe the answer is:
recital
'concert' is the definition.
(thesaurus)
'not now recalled involving contralto and i' is the wordplay.
'not now' becomes 'later' (I've seen this before).
'recalled' says the letters should be written backwards.
'involving' is an insertion indicator.
'contralto' becomes 'c' (musical abbreviation).
'and' is a charade indicator (letters next to each other).
'later' written backwards gives 'retal'.
'c'+'i'='ci'
'retal' placed around 'ci' is 'RECITAL'.
(Other definitions for recital that I've seen before include "Public musical performance" , "Public performance by a solo musician" , "Solo music performance" , "Public performance of music" , "Musician's performance" .)