Secure locks with this chief musical group (8)
I believe the answer is:
headband
'secure locks with this chief musical group' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'with this chief musical group' is the wordplay.
'with' says to put letters next to each other.
'this chief' becomes 'head' (synonyms).
'musical group' becomes 'band' (band is a kind of musical group).
'head'+'band' is 'HEADBAND'.
Can you help me to learn more?
(Other definitions for headband that I've seen before include "Ribbon worn on top" , "fillet" , "Something to secure the hair" .)