Endlessly carry small child (3)
I believe the answer is:
tot
'small child' is the definition.
(tot can mean a baby or toddler)
'endlessly carry' is the wordplay.
'endlessly' means to remove the last letter.
'carry' becomes 'tote' (toting is a kind of carrying).
'tote' with its final letter removed is 'TOT'.
(Other definitions for tot that I've seen before include "Small drink; accumulate" , "slug?" , "Small baby" , "Tiny child" , "Small quantity of alcoholic drink" .)