Vim or vigor (3)
I believe the answer is:
pep
I believe this clue is a double definition.
'vim' is the first definition.
(I've seen this in another clue)
'vigor' is the second definition.
(I've seen this in another clue)
(Other definitions for pep that I've seen before include "Palindromic vim and vigour" , "Palindrome for vitality or energy" , "Go" , "Palindrome for vigour" , "Vim and vitality" .)