Rose spreading around one American grave (7)
I believe the answer is:
serious
'grave' is the definition.
(I know that grave can be written as serious)
'rose spreading around one american' is the wordplay.
'spreading' indicates an anagram.
'around' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'american' becomes 'US' (United States).
'rose' anagrammed gives 'sero'.
'sero' going around 'i' is 'serio'.
'serio'+'us'='SERIOUS'
(Other definitions for serious that I've seen before include "Earnest, sincere" , "Earnest; vital" , "Not light or frivolous" , "Earnest - important" , "Important -- grave" .)