Lock service that's replayed after call (7)
I believe the answer is:
ringlet
'lock' is the definition.
(both can mean a piece of someone's hair)
'service that's replayed after call' is the wordplay.
I cannot quite see how this works, but
'service' could be 'let' (type of tennis serve) and 'let' is present in the answer.
'call' could be 'ring' (synonyms) and 'ring' is present in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for ringlet that I've seen before include "Curl of hair; butterfly" , "Curl or tendril" , "Curling lock of hair" , "A curl - kind of tingler" , "Cluster of hair" .)