Parent with head lowered getting tot up (3)
I believe the answer is:
add
'tot up' is the definition.
(synonyms)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for add that I've seen before include "Include" , "problem for hyperactive children" , "Give more" , "put two and two together" , "Put together - append" .)