Exonerate half of rock band then leave (6)
I believe the answer is:
acquit
'exonerate' is the definition.
(synonyms)
'half of rock band then leave' is the wordplay.
'half of rock band' becomes 'ac' (I can't justify this - if you can you should believe this answer much more).
'then' means one lot of letters go next to another.
'leave' becomes 'quit' (quitting is a kind of leaving).
'ac'+'quit'='ACQUIT'
Can you help me to learn more?
(Other definitions for acquit that I've seen before include "Exonerate" , "Free - act" , "Group of families" , "Discharge as innocent, dismiss charge" , "Find not guilty" .)