Head start on earlier container (6)
I believe the answer is:
holder
'container' is the definition.
(I know that container can be written as holder)
'head start on earlier' is the wordplay.
'start on' suggests taking the first letters (I've seen 'starts on' mean this).
'earlier' becomes 'older' ('old' can be similar in meaning to 'early').
The first letter of 'head' is 'h'.
'h'+'older'='HOLDER'
(Other definitions for holder that I've seen before include "Noddy" , "retainer" , "Occupant" , "Something which grasps" , "Keeper; container" .)