One day California will supply an entire continent (6)
I believe the answer is:
africa
'an entire continent' is the definition.
'africa' can be an answer for 'continent' (Africa is an example). I'm not certain of the 'an entire' bit.
'one day california' is the wordplay.
'one' becomes 'a'.
'day' becomes 'fri' (abbreviation for Friday).
'california' becomes 'ca'.
'a'+'fri'+'ca'='AFRICA'
'will supply' is the link.
Can you help me to learn more?
(Other definitions for africa that I've seen before include "RAF and CIA strangely together on the continent" , "Out of -, novel by Karen Blixen (filmed)" , "Second largest continent" , "Continent for 21 Down" , "Out of . . . . . . (film) (6)" .)