Deal effectively with the bishop's garb (4)
I believe the answer is:
cope
'deal' is the definition.
(synonyms)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for cope that I've seen before include "Manage, subsist" , "Vestment; get along" , "Clerical vestment; to deal (with)" , "Deal with, manage ok" , "Deal effectively (with a difficulty)" .)