Fanatical attack captures bishop (5)
I believe the answer is:
rabid
'fanatical' is the definition.
(synonyms)
'attack captures bishop' is the wordplay.
'attack' becomes 'raid' (raiding is a kind of attacking).
'captures' indicates putting letters inside.
'bishop' becomes 'b' (abbreviation used in chess).
'raid' enclosing 'b' is 'RABID'.
(Other definitions for rabid that I've seen before include "Extremely fanatical" , "Ill from a mad dog bite?" , "Extreme, fanatical" , "Zealous" , "Furious like mad dog?" .)