Go up again (3)
I believe the answer is:
pep
'go' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for pep that I've seen before include "Go" , "Palindrome for vitality or energy" , "Palindrome for vigour" , "Palindromic vim and vigour" , "Energy or enthusiasm" .)