Hide at one time found in California (7)
I believe the answer is:
conceal
'hide' is the definition.
(I know that hide can be written as conceal)
'one time found in california' is the wordplay.
'one time' becomes 'once' (synonyms).
'found in' means one lot of letters goes inside another.
'california' becomes 'cal' (short for California).
'once' going inside 'cal' is 'CONCEAL'.
'at' acts as a link.
(Other definitions for conceal that I've seen before include "Hide, cover" , "Screen" , "Keep out of sight" , "hush up!" , "'Hide, keep secret (7)'" .)