Healing group led by copper (6)
I believe the answer is:
curing
'healing' is the definition.
('cure' can be a synonym of 'heal')
'group led by copper' is the wordplay.
'group' becomes 'ring'.
'led by' says to put letters next to each other.
'copper' becomes 'cu' (chemical symbol).
'ring' after 'cu' is 'CURING'.
(Other definitions for curing that I've seen before include "Smoking" , "Preserving fish, meat, etc" , "putting things right" , "Making better" , "Preserving meat or making well again" .)