Cool out and it’s the end of August (7)
I believe the answer is:
distant
'cool' is the definition.
('distant' can be similar in meaning to 'cool')
'out and it's the end of august' is the wordplay.
'out' indicates anagramming the letters.
'the end of' indicates one should take the final letters.
The final letter of 'august' is 't'.
'and'+'its'='andits'
'andits' with letters rearranged 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" .)