Stunning canyon. Love America! (8)
I believe the answer is:
gorgeous
'stunning' is the definition.
(I've seen this before)
'canyon love america' is the wordplay.
'canyon' becomes 'gorge' (I've seen this in another clue).
'love' becomes 'o' (love means zero in tennis).
'america' becomes 'US' (United States).
'gorge'+'o'+'us'='GORGEOUS'
(Other definitions for gorgeous that I've seen before include "Beautiful - glorious" , "Richly coloured, magnificent" , "Very attractive" , "Lovely" , "Showy" .)