Quick to hide damage, drug dealer (8)
I believe the answer is:
pharmacy
'drug dealer' is the definition.
(I've seen this before)
'quick to hide damage' is the wordplay.
'quick' becomes 'pacy'.
'to hide' indicates putting letters inside.
'damage' becomes 'harm' ('harm' can be a synonym of 'damage').
'pacy' enclosing 'harm' is 'PHARMACY'.
(Other definitions for pharmacy that I've seen before include "Science of dispensing drugs" , "Business" , "It supplies drugs" , "Where drugs are dispensed" , "Medical establishment" .)