Father started packing at half past (4)
I believe the answer is:
'father' is the definition.
(I know that father can be written as papa)
'started packing at half past' is the wordplay.
'started' says to take the initial letters.
'half' means to take half the letters.
The first letters of 'packing at' is 'pa'.
'past' halved is 'pa'.
(Other definitions for papa that I've seen before include "The old man" , "Father; P (radio comms.)" , "Father; letter P" , "Mama's other half?" , "Comms code for 'P'" .)