Go out of shape, perhaps (3)
I believe the answer is:
pep
'go' is the definition.
(both can mean energy or vitality)
'of shape perhaps' is the wordplay.
'of' indicates the answer is hidden within the clue.
'PEP' can be found hidden inside 'shape perhaps'.
'out' is the link.
(Other definitions for pep that I've seen before include "Palindromic vim and vigour" , "Ginger; tax-free investment" , "Palindrome for vigour" , "Palindromic energy or vim" , "Energy, liveliness" .)