Missed stroke, as atmosphere’s sweltering (3,4)
I believe the answer is:
'missed stroke' is the definition.
(a missed attempt to hit a ball)
'atmosphere's sweltering' is the wordplay.
'atmosphere's' becomes 'air's' ('air' can be a synonym of 'atmosphere').
'sweltering' becomes 'hot' (similar in meaning).
'as' acts as a link.
(Another definition for air shot that I've seen is " Golf stroke that misses the ball".)