Rock outside broadcast, daughter is backing Dury, perhaps (8)
I believe the answer is:
obsidian
'rock' is the definition.
(I know that obsidian is a type of volcanic glass)
'outside broadcast daughter is backing dury perhaps' is the wordplay.
I cannot really understand how this works, but
'broadcast' could be 'ob' (I've seen this in other clues) and 'ob' is found in the answer.
'daughter' could be 'd' (genealogical abbreviation) and 'd' is found in the answer.
'is' could be 'ii' (more than one I) and 'ii' is present in the leftover letters.
The remaining letters 'san' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for obsidian that I've seen before include "A glassy volcanic rock" , "Glass bottle may be in this" , "Dark volcanic glass" , "Volcanic glass-like rock" , "Dark volcanic rock" .)