Working hard, I must keep time, being busy (2,3,2)
I believe the answer is:
on the go
'being busy' is the definition.
(similar in meaning)
'working hard i must keep time' is the wordplay.
'working' becomes 'on' (on can mean working or activated).
'hard' becomes 'h' (abbreviation used in pencil classifications).
'i' becomes 'ego' ('I' in Latin).
'must keep' is an insertion indicator.
'time' becomes 't' (abbreviation).
'on'+'h'+'ego'='onhego'
'onhego' going around 't' is 'ON THE GO'.
(Other definitions for on the go that I've seen before include "Running around busily" , "Keeping busy, not stopping" , "Always busy" , "Moving -- active" , "Active, always doing something" .)