Child gets out of bed to do sums (3,2)
I believe the answer is:
tot up
'to do sums' is the definition.
I can't judge whether this definition defines the answer.
'child gets out of bed' is the wordplay.
'child' becomes 'tot' (term for a young child).
'gets' says to put letters next to each other.
'out of bed' becomes 'up' (synonyms).
'tot'+'up'='TOT UP'
Can you help me to learn more?
(Other definitions for tot up that I've seen before include "Do summer job" , "Add (some numbers)" , "Sum - total" , "Tally" , "Reckon" .)