Taken in by national leader? One hundred per cent! (3)
I believe the answer is:
all
'hundred per cent' is the definition.
I can't judge whether this definition defines the answer.
'taken in by national leader? one' is the wordplay.
'taken in by' indicates the answer is hidden within the clue.
'ALL' can be found hidden inside 'national leader one'.
Can you help me to learn more?
(Other definitions for all that I've seen before include "'... things come to those who wait'" , "Garden passage between trees or bushes" , "that's as many as there are" , "Completely, everything" , "Passage in a formal garden" .)