Initially, Alexander's charming (5)
I believe the answer is:
acute
'initially alexander's charming' is the definition.
I can't judge whether this defines the answer.
'initially alexander's charming' is the wordplay.
'initially' says to take the initial letters.
'charming' becomes 'cute' (I've seen this before).
The initial letter of 'alexanders' is 'a'.
'a'+'cute'='ACUTE'
(Other definitions for acute that I've seen before include "Shrewd; severe" , "quick on the uptake" , "Sharp like angle" , "Sharp, angle or mind" , "Very perceptive, having sharp mind" .)