Lock enclosed by covering letter (7)
I believe the answer is:
ringlet
'lock' is the definition.
(both can mean a piece of someone's hair)
'enclosed by covering letter' is the wordplay.
'RINGLET' is hidden in amongst the letters.
But, I'm not sure how this is indicated.
Can you help me to learn more?
(Other definitions for ringlet that I've seen before include "Handy device" , "Hair feature" , "twist of sorts?" , "Curling lock of hair" , "Cluster of hair" .)