Rock band I love is playing (8)
I believe the answer is:
obsidian
'rock' is the definition.
(I know that Obsidian is a type of volcanic rock)
'band i love is playing' is the wordplay.
'love' becomes 'o' (love means zero in tennis).
'playing' indicates an anagram.
'band'+'i'+'o'+'is'='bandiois'
'bandiois' is an anagram of 'OBSIDIAN'.
(Other definitions for obsidian that I've seen before include "Dark volcanic rock" , "A hard black volcanic glass" , "Dark glass-like rock" , "Dark glassy rock formed from lava" , "Dark volcanic glass" .)