Twisting of antlers or of breastbone (7)
I believe the answer is:
sternal
'of breastbone' is the definition.
(I've seen this before)
'twisting of antlers' is the wordplay.
'antlers' can be anagrammed to 'STERNAL'.
But, I am unsure how this is indicated.
'or' is the link.
Can you help me to learn more?
(Other definitions for sternal that I've seen before include "of breastbone" , "of chest" .)