Summit meeting’s principle bores expert (4)
I believe the answer is:
acme
'summit' is the definition.
(synonyms)
'meeting's principle bores expert' is the wordplay.
'meeting's principle' becomes 'm' (I can't explain this - if you can you should give a lot more credence to this answer).
'bores' is an insertion indicator (bore can mean to drill into).
'expert' becomes 'ace' (ace can informally mean very good).
'm' put inside 'ace' is 'ACME'.
Can you help me to learn more?
(Other definitions for acme that I've seen before include "Top; peak" , "Highest stage of development" , "High point of excellence" , "Highest point (of something)" , "'Highest point, apex (4)'" .)