Was I not AB? Perhaps I was! (9)
I believe the answer is:
boatswain
'i was' is the definition.
I can't tell whether this defines the answer.
'was i not ab? perhaps' is the wordplay.
'perhaps' indicates anagramming the letters.
'was'+'i'+'not'+'ab'='wasinotab'
'wasinotab' is an anagram of 'BOATSWAIN'.
Can you help me to learn more?
(Other definitions for boatswain that I've seen before include "A fully developed bo'sun" , "Merchant ship's petty officer" , "I was not AB (anag) - naval warrant officer" , "One at sea" , "Warrant officer in charge of a ship's crew" .)