Confirm Mark is touring the States (7)
I believe the answer is:
sustain
'confirm' is the definition.
(synonyms)
'mark is touring the states' is the wordplay.
'mark' becomes 'stain' (synonyms).
'is touring' indicates putting letters inside (touring can mean going round).
'the states' becomes 'us' (abbreviation for the United States).
'stain' placed around 'us' is 'SUSTAIN'.
(Other definitions for sustain that I've seen before include "Maintain" , "Nurture, uphold" , "Bear (something's weight)" , "Support, keep going" , "Withstand" .)