Though having examined carefully, was taken in by (6)
I believe the answer is:
conned
'by' is the definition.
The answer and definition are different parts of speech. However, past participle verbs and adjectives occasionally mean the same thing.
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for conned that I've seen before include "Studied; cheated" , "Deceived" , "Taken in, tricked" , "Studied carefully" .)