Pep has been cavorting outside. Get away! (6)
I believe the answer is:
begone
'get away' is the definition.
(command to be gone)
'pep has been cavorting outside' is the wordplay.
I cannot quite understand how this works, but
'pep' could be 'go' (both can mean energy or vitality) and 'go' is found within the answer.
an anagram of 'been' is 'bene' which is present in the left over letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for begone that I've seen before include "Archaic command to buzz off" , "shove off" , "get lost" , "Get away" , "make himself scarce" .)