Summit meeting’s introduction: up to nation to be prepared (11)
I believe the answer is:
mountaintop
'summit' is the definition.
(thesaurus)
'meeting's introduction up to nation to be prepared' is the wordplay.
'introduction' indicates taking the first letters.
'to be prepared' indicates anagramming the letters.
The initial letter of 'meetings' is 'm'.
'up'+'to'+'nation'='uptonation'
'uptonation' anagrammed gives 'ountaintop'.
'm'+'ountaintop'='MOUNTAINTOP'
(Other definitions for mountaintop that I've seen before include "Highest place for miles around" , "Located on a peak" .)