Not quite right in previous performance (7)
I believe the answer is:
inexact
'not quite right' is the definition.
(I've seen this before)
'in previous performance' is the wordplay.
'previous' becomes 'ex' (I've seen this in other clues).
'performance' becomes 'act' (act is a kind of performance).
'in'+'ex'+'act'='INEXACT'
(Other definitions for inexact that I've seen before include "Fuzzy - untrue" , "Not precise, approximate" , "Lax" , "Not quite right" , "Nice tax (anag) - approximate" .)