Named everyone locked in by church key (6)
I believe the answer is:
called
'named' is the definition.
(synonyms)
'everyone locked in by church key' is the wordplay.
'everyone' becomes 'all' (all people).
'locked in' means one lot of letters goes inside another.
'by' means one lot of letters go next to another.
'church' becomes 'CE' (abbreviation for Church of England).
'key' becomes 'd' (musical key).
'ce' put next to 'd' is 'ced'.
'all' inserted within 'ced' is 'CALLED'.
(Other definitions for called that I've seen before include "Phoned or visited" , "Having a specified name" , "Named" , "Came to visit" , "Summoned or phoned" .)