Cross made by removing ends of protective jewel (4)
I believe the answer is:
mule
'cross' is the definition.
(a mule is a cross of a donkey and a horse)
'removing ends of protective jewel' is the wordplay.
'removing ends of' says to take the centre (the end letters are removed).
'protective jewel' becomes 'amulet' (piece of jewellery providing magical protection).
The middle of 'amulet' is 'MULE'.
'made by' acts as a link.
(Other definitions for mule that I've seen before include "Drug courier; animal" , "Equine hybrid" , "Obstinate creature" , "Illegal drugs courier" , "Drug smuggler" .)