Bar advanced during mass (5)
I believe the answer is:
baulk
'bar' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe there's an association between them I don't understand?
'advanced during mass' is the wordplay.
'advanced' becomes 'a' (abbreviation).
'during' is an insertion indicator.
'mass' becomes 'bulk' (bulk can mean a mass of something).
'a' inserted into 'bulk' is 'BAULK'.
Can you help me to learn more?
(Other definitions for baulk that I've seen before include "Jib" , "Resist, demur" .)