Breeze in blazing sun relaxes (7)
I believe the answer is:
unwinds
'relaxes' is the definition.
('unwind' can be a synonym of 'relax')
'breeze in blazing sun' is the wordplay.
'breeze' becomes 'wind' (I've seen this before).
'in' means one lot of letters goes inside another.
'blazing' indicates an anagram (I've seen this in other clues).
'sun' anagrammed gives 'uns'.
'wind' put into 'uns' is 'UNWINDS'.
(Other definitions for unwinds that I've seen before include "Rests and becomes less tense" , "Becomes less tense and relaxes" , "Relaxes; pays out (thread)" .)