California gets back lock for performer (7)
I believe the answer is:
actress
'performer' is the definition.
(actress is a kind of performer)
'california gets back lock' is the wordplay.
'california' becomes 'ca'.
'gets back' says the letters should be written in reverse (I've seen 'got back' mean this).
'lock' becomes 'tress' (I've seen this before).
'ca' backwards is 'ac'.
'ac'+'tress'='ACTRESS'
'for' acts as a link.
(Other definitions for actress that I've seen before include "One on stage" , "One playing" , "Female stage-player" , "Stage performer" , "eg Emma Thompson" .)