American in GTO shows appreciation (5)
I believe the answer is:
gusto
'appreciation' is the definition.
(thesaurus)
'american in gto' is the wordplay.
'american' becomes 'us'.
'in' indicates putting letters inside.
'us' inserted inside 'gto' is 'GUSTO'.
'shows' acts as a link.
(Other definitions for gusto that I've seen before include "Energy" , "Zest and enjoyment in doing something" , "Zest, great enjoyment in doing" , "Vigorous enthusiasm" , "Zest, pleasure in action" .)