Using bad language about old type of hunting (8)
I believe the answer is:
Here is my best explanation:
'type of hunting' is the definition.
'using bad language about old' is the subsidiary indication.
'using bad language' becomes 'cursing' (I've seen this before).
'about' means one lot of letters goes inside another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'cursing' placed around 'o' is 'coursing'.
(Other definitions for coursing that I've seen before include "blood sport", "it can be fatal for hares", "illegal hunting?", "Hunting with dogs" and "Running".)