Cool out and it's the end of August (7)
I believe the answer is:
distant
'cool' is the definition.
(similar in meaning)
'out and it's the end of august' is the wordplay.
'out' is an anagram indicator.
'the end of' indicates one should take the final letters.
The final letter of 'august' is 't'.
'and'+'its'='andits'
'andits' anagrammed gives 'distan'.
'distan'+'t'='DISTANT'
(Other definitions for distant that I've seen before include "Far apart in space or time" , "Aloof" , "overseas?" , "Absent - coming from a far-away place" , "Far away" .)