Still, air provides a service (8)
I believe the answer is:
evensong
'a service' is the definition.
(type of church service)
'still air' is the wordplay.
'still' becomes 'even' (synonyms).
'air' becomes 'song' (air can mean a piece of music).
'even'+'song'='EVENSONG'
'provides' acts as a link.
(Other definitions for evensong that I've seen before include "... Prayers" , "Religious service" , "Late afternoon church service" , "Church service late in the day" , "6 [SERVICE] ?" .)