Lecturer at church has code which unlocks the door (8)
I believe the answer is:
latchkey
'code which unlocks the door' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'lecturer at church has' is the wordplay.
'lecturer' becomes 'l' (abbreviation for lecturer).
'church' becomes 'ch' (abbreviation on maps etc).
'has' becomes 'key' (I can't explain this - if you can you should give a lot more credence to this answer).
'l'+'at'+'ch'+'key'='LATCHKEY'
Can you help me to learn more?
(Other definitions for latchkey that I've seen before include "Common device to open outer door" , "A supposed freedom from domestic restrictions" , "Sort of self-reliant child" , "Describes a child who returns to an empty home" , "Front door opener (for children with absent parents?)" .)