Little kid, a learner getting sum (5)
I believe the answer is:
total
'sum' is the definition.
(I know that sum can be written as total)
'little kid a learner getting' is the wordplay.
'little kid' becomes 'tot' (tot can mean a young child).
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
'getting' is a charade indicator (letters next to each other).
'tot'+'a'+'l'='TOTAL'
(Other definitions for total that I've seen before include "Unqualified" , "Aggregate amount" , "Full, entire amount" , "Complete, absolute" , "The whole, sum" .)