Maybe cool for half an hour in the shade (6)
I believe the answer is:
colour
'shade' is the definition.
(I've seen this before)
'maybe cool for half an hour' is the wordplay.
'maybe' indicates anagramming the letters.
'for' is a charade indicator (letters next to each other).
'half an' suggests halving the letters.
'hour' cut in half is 'ur'.
'cool' is an anagram of 'colo'.
'colo'+'ur'='COLOUR'
'in the' acts as a link.
(Other definitions for colour that I've seen before include "black?" , "Distort; blush; hue" , "See 10" , "'Tinge, hue (6)'" , "Go red" .)