Not the northern summit, say (5)
I believe the answer is:
speak
'say' is the definition.
(synonyms)
'not the northern summit' is the wordplay.
I cannot quite see how this works, but
'summit' could be 'peak' (mountain peak) and 'peak' is located in the answer.
A single letter 's' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for speak that I've seen before include "Say something" , "Utter words" , "Orate" , "Talk" , "give a lecture" .)