Here's another (stunningly fast) way (albeit limited to 256 rows):
SELECT country
, clicks
, FIND_IN_SET(clicks,(SELECT GROUP_CONCAT(DISTINCT clicks ORDER BY clicks DESC) FROM country_clicks)) rank
FROM country_clicks
or, if you prefer...
SELECT FIND_IN_SET(clicks,(SELECT GROUP_CONCAT(DISTINCT clicks ORDER BY clicks DESC) FROM country_clicks)) rank
FROM country_clicks
WHERE country = 45;