Exaggeration about California, say, intended to be heard (13)
I believe the answer is:
overstatement
'exaggeration' is the definition.
(I know that exaggeration can be written as overstatement)
'about california say intended to be heard' is the wordplay.
'about' becomes 'over' (both can mean around).
'california say' becomes 'state' (California is a US state).
'intended' becomes 'meant' (to mean something is to intend it).
'to be heard' shows a homophone (sound like).
'meant' is a homophone of 'ment'.
'over'+'state'+'ment'='OVERSTATEMENT'
(Other definitions for overstatement that I've seen before include "Hyperbole" , "Exaggeration" .)