Golf setter played when putting in America, most impressive (8)
I believe the answer is:
greatest
'most impressive' is the definition.
'golf setter played when putting in' is the wordplay.
'golf' becomes 'g' (phonetic alphabet: alpha, bravo, charlie etc.).
'played' indicates an anagram.
'when' becomes 'a' (I can't explain this - if you can you should believe this answer much more).
'putting in' is an insertion indicator.
'setter' is an anagram of 'retest'.
'retest' enclosing 'a' is 'reatest'.
'g'+'reatest'='GREATEST'
'america' is the link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for greatest that I've seen before include "Unsurpassable" , "Most celebrated" , "Biggest and best, like Muhammad Ali" , "Unsurpassed" , "Most important!" .)