Security device left at church (5)
I believe the answer is:
latch
'security device' is the definition.
'latch' can be an answer for 'device' (latch is a kind of device). I am not certain of the 'security' bit.
'left at church' is the wordplay.
'left' becomes 'l' (common abbreviation).
'church' becomes 'ch' (common abbreviation).
'l'+'at'+'ch'='LATCH'
Can you help me to learn more?
(Other definitions for latch that I've seen before include "Small bar for fastening a door" , "Something to secure" , "Door catch" , "Gate fastener" , "Device to hold door shut" .)