Something stimulating to do up (3)
I believe the answer is:
pep
'do up' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for pep that I've seen before include "Vim and vitality" , "Go" , "Energy, liveliness" , "Energy, zip" , "Palindrome for vitality or energy" .)