Dark rock band with B-side lacking energy, Mr Thorpe (8)
I believe the answer is:
obsidian
'dark rock' is the definition.
'obsidian' can be an answer for 'rock' (obsidian is a kind of rock). I am unsure of the 'dark' bit.
'band with b-side lacking energy mr thorpe' is the wordplay.
'band' becomes 'o' (I've seen this in other clues).
'with' says to put letters next to each other.
'lacking' is a deletion indicator.
'energy' becomes 'e' (physics symbol as in E=mc2).
'mr thorpe' becomes 'Ian' (Ian Thorpe is an Australian swimmer).
'side' with 'e' removed is 'sid'.
'o'+'b'+'sid'+'ian'='OBSIDIAN'
Can you help me to learn more?
(Other definitions for obsidian that I've seen before include "Dark volcanic rock" , "A hard black volcanic glass" , "Dark volcanic glass" , "Volcanic glass-like rock" , "Glass bottle may be in this" .)