Impressive meow as Siamese at last moves (7)
I believe the answer is:
awesome
'impressive' is the definition.
(similar in meaning)
'meow as siamese at last moves' is the wordplay.
'at last' suggests the final letters.
'moves' indicates an anagram.
The last letter of 'siamese' is 'e'.
'meow'+'as'+'e'='meowase'
'meowase' anagrammed gives 'AWESOME'.
(Other definitions for awesome that I've seen before include "Totally cool!" , "Inspiring reverence mixed with fear" , "staggering" , "Inspiring reverential fear" , "wizard" .)