Exonerate a bishop taking crack (7)
I believe the answer is:
absolve
'exonerate' is the definition.
(thesaurus)
'a bishop taking crack' is the wordplay.
'bishop' becomes 'b' (abbreviation used in chess).
'taking' is a charade indicator (letters next to each other).
'crack' becomes 'solve' (I've seen this before).
'a'+'b'+'solve'='ABSOLVE'
(Other definitions for absolve that I've seen before include "Grant pardon for" , "Exonerate" , "Declare (someone) guilt-free" , "Declare (someone) blameless" , "Exculpate" .)