Youngster with whom I'm leaving California shortly (4)
I believe the answer is:
calf
'youngster' is the definition.
(I've seen this before)
'whom i'm leaving california shortly' is the wordplay.
I cannot quite understand how this works, but
'california' could be 'cal' (short for California) and 'cal' is found in the answer.
A single letter 'f' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'with' is the link.
Can you help me to learn more?
(Other definitions for calf that I've seen before include "Young cow or bull" , "Young animal associated with soft leather" , "Is it above the ankle" , "Young cow - part of the leg" , "Young animal - part of leg" .)