Superior, British in flying boat (5)
I believe the answer is:
abbot
'superior' is the definition.
(abbot is a kind of superior)
'british in flying boat' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'in' means one lot of letters goes inside another.
'flying' is an anagram indicator.
'boat' with letters rearranged gives 'abot'.
'b' placed inside 'abot' is 'ABBOT'.
(Other definitions for abbot that I've seen before include "Head of a religious community" , "Superior monk" , "Senior monk" , "Head of group of monks" , "Monastic chief" .)