Go in hope, positively (3)
I believe the answer is:
pep
'go' is the definition.
(I've seen this in another clue)
'in hope positively' is the wordplay.
'in' says the answer is hidden in the clue.
'PEP' is hidden within 'hope positively'.
(Other definitions for pep that I've seen before include "Go" , "Palindromic energy or vim" , "Energy or enthusiasm" , "Get-up-and-go" , "Palindromic vim and vigour" .)