Healing dog by performing Evita (8)
I believe the answer is:
curative
'healing' is the definition.
(I know that healing can be written as curative)
'dog by performing evita' is the wordplay.
'dog' becomes 'cur' (a cur is an aggressive or scruffy dog).
'by' says to put letters next to each other.
'performing' is an anagram indicator (the letters move around or 'perform').
'evita' with letters rearranged gives 'ative'.
'cur'+'ative'='CURATIVE'
(Other definitions for curative that I've seen before include "Restoring to health" , "Healing" , "Medicine" , "health-giving" , "Therapeutic" .)