Take a nip across summit? Come again? (5,2)
I believe the answer is:
speak up
'come again?' is the definition.
(I've seen this in another clue)
'take a nip across summit?' is the wordplay.
'take a nip' becomes 'sup' (I am not sure about this - if you are sure you should believe this answer much more).
'across' indicates putting letters inside.
'summit?' becomes 'peak' (mountain peak).
'sup' placed around 'peak' is 'SPEAK UP'.
Can you help me to learn more?
(Other definitions for speak up that I've seen before include "Talk louder, can't hear you" , "give opinions boldly" , "Raise one's voice" , "augment volume" , "Make oneself heard" .)