Packed it all in is what it amounted to (8)
I believe the answer is:
totalled
'what it amounted to' is the definition.
I can't judge whether this definition defines the answer.
'packed it all in' is the wordplay.
'packed' becomes 'toed' (I can't explain this - if you can you should give a lot more credence to this answer).
'it' becomes ''t' (abbreviation. e.g. in 'tis).
'in' is an insertion indicator.
't'+'all'='tall'
'toed' going around 'tall' is 'TOTALLED'.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for totalled that I've seen before include "Added together" , "completely destroyed" , "came to" , "Determined the sum of" , "blown away" .)