Relish; vigour (5)
I believe the answer is:
gusto
I believe this clue is a double definition.
'relish' is the first definition.
(I know that relish can be written as gusto)
'vigour' is the second definition.
(I've seen this before)
(Other definitions for gusto that I've seen before include "Zest, zeal" , "Hearty enjoyment" , "Great enjoyment in doing something" , "Relish - zest" , "exhilaration" .)