Wrong girl nearly grabbed (8)
I believe the answer is:
mistaken
'wrong' is the definition.
(similar in meaning)
'girl nearly grabbed' is the wordplay.
'girl' becomes 'miss' (term of address for an unmarried woman).
'nearly' means to remove the last letter.
'grabbed' becomes 'taken' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'miss' with its last letter removed is 'mis'.
'mis'+'taken'='MISTAKEN'
Can you help me to learn more?
(Other definitions for mistaken that I've seen before include "Wrongly understood" , "In error in mankiest way" , "Wrong in opinion, judgment etc." , "'Wrong, misguided (8)'" , "Wrong, incorrect" .)