One with roots in California a US agency arrests (6)
I believe the answer is:
acacia
'one with roots' is the definition.
I can't judge whether this definition defines the answer.
'california a us agency arrests' is the wordplay.
'california' becomes 'CA' (abbreviation).
'us agency' becomes 'cia' (I've seen this before).
'arrests' is an insertion indicator (inserted letters are contained or arrested).
'a'+'cia'='acia'
'ca' going within 'acia' is 'ACACIA'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for acacia that I've seen before include "Thorny flowering shrub" , "Thorny tree, wattle" , "Type of shrub or tree" , "(Sub)tropical shrub with yellow or white flowers - wattle" , "Spiny tree or shrub" .)