Child, a learner to be given sum (5)
I believe the answer is:
total
'sum' is the definition.
('total' can be a synonym of 'sum')
'child a learner to be given' is the wordplay.
'child' becomes 'tot' (I've seen this before).
'learner' becomes 'l'.
'to be given' is a charade indicator (letters next to each other).
'tot'+'a'+'l'='TOTAL'
(Other definitions for total that I've seen before include "Everything added together" , "Not qualified" , "Entirety" , "The whole number" , "to give the final figure" .)