Stuffy sort of serials (7)
I believe the answer is:
airless
'stuffy' is the definition.
(stuffy means lacking ventilation)
'sort of serials' is the wordplay.
'sort of' indicates anagramming the letters.
'serials' with letters rearranged gives 'AIRLESS'.
(Other definitions for airless that I've seen before include "Stifling" , "not a breath of wind" , "Close" , "Very stuffy" , "Not ventilated" .)