Rising stars around independent channel (5)
I believe the answer is:
sinus
'channel' is the definition.
(I know that sinus is a type of channel)
'rising stars around independent' is the wordplay.
'rising' is a reversal indicator (going up in a down clue).
'stars' becomes 'Suns' (suns are stars).
'around' indicates putting letters inside.
'independent' becomes 'i'.
'suns' enclosing 'i' is 'sunis'.
'sunis' in reverse letter order is 'SINUS'.
(Other definitions for sinus that I've seen before include "Air cavity in the cranial bones" , "Anatomical cavity" , "Bodily cavity" , "Cavity in the facial bones" , "Cavity within a bone" .)