Feeling smart, is taking lessons (9)
I believe the answer is:
intuition
'feeling' is the definition.
(intuition is a kind of feeling)
'smart is taking lessons' is the wordplay.
'smart' becomes 'in' (as in fashionable).
'is taking' says to put letters next to each other.
'lessons' becomes 'tuition' (I've seen this before).
'in'+'tuition'='INTUITION'
(Other definitions for intuition that I've seen before include "Ability to understand immediately" , "women are known for it" , "Perception" , "an instinctive thing" , "Unjustified belief" .)