Superior bishop in boat, adrift (5)
I believe the answer is:
abbot
'superior' is the definition.
(abbot is a kind of superior)
'bishop in boat adrift' is the wordplay.
'bishop' becomes 'b' (abbreviation used in chess).
'in' is an insertion indicator.
'adrift' indicates anagramming the letters.
'boat' with letters rearranged gives 'abot'.
'b' placed into 'abot' is 'ABBOT'.
(Other definitions for abbot that I've seen before include "Brother" , "meeting Newton in Devon" , "Head monk" , "first in order" , "Head of abbey" .)