Lead first of children into English class (6)
I believe the answer is:
Here is my best explanation:
'lead' is the definition.
'first of children into english class' is the subsidiary indication.
'first of' suggests taking the first letters.
'into' is an insertion indicator.
'english' becomes 'e' (abbreviation).
'class' becomes 'sort' ('sort' can be a synonym of 'class'**).
The first letter of 'children' is 'c'.
'c' placed into 'esort' is 'escort'.
(Other definitions for escort that I've seen before include "Provide company - car - attendant", "Bodyguard", "Act as companion, attend", "One who accompanies another", "Protective accompaniment", "Companion (perhaps paid)", "Companion: train", "Person who accompanies or guards another", "Entourage" and "One who accompanies, for protection or as an honour".)