Performer has power lock (7)
I believe the answer is:
actress
'performer' is the definition.
(I know that performer can be written as actress)
'power lock' is the wordplay.
'power' becomes 'AC' (AC is an example).
'lock' becomes 'tress' (both can mean a piece of hair).
'ac'+'tress'='ACTRESS'
'has' acts as a link.
(Other definitions for actress that I've seen before include "Female in plays/films" , "Female thespian" , "Female player" , "Casters (anag.)" , "I might work in Hollywood" .)