Wizard stops old man being harmed (7)
I believe the answer is:
damaged
'being harmed' is the definition.
(I've seen this before)
'wizard stops old man' is the wordplay.
'wizard' becomes 'mage' ().
'stops' indicates putting letters inside.
'old man' becomes 'dad' (synonyms).
'mage' going within 'dad' is 'DAMAGED'.
(Other definitions for damaged that I've seen before include "Marred" , "Flawed, harmed" , "Impaired" , "Harmed, injured or spoiled" , "Sullied or harmed" .)