Go and reciprocate (3)
I believe the answer is:
pep
'go' is the definition.
(thesaurus)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for pep that I've seen before include "Go" , "Energy or enthusiasm" , "savings plan" , "Get-up-and-go" , "Palindromic vim and vigour" .)