Air is inferior, leading to gasping (10)
I believe the answer is:
breathless
'gasping' is the definition.
(similar in meaning)
'air is inferior leading' is the wordplay.
'air' becomes 'breath' (breath is a kind of air).
'is inferior' becomes 'less' (lesser or less significant).
'leading' is a charade indicator (letters next to each other).
'breath'+'less'='BREATHLESS'
'to' acts as a link.
(Other definitions for breathless that I've seen before include "Still" , "panting?" , "Short-winded" , "Spent" , "Gasping for air" .)