Stars constantly yattering about Brazilian port (5)
I believe the answer is:
orion
'stars' is the definition.
(I've seen this before)
'constantly yattering about brazilian port' is the wordplay.
'constantly yattering' becomes 'on' (as in going on about something).
'about' is an insertion indicator.
'brazilian port' becomes 'rio' (I've seen this before).
'on' going around 'rio' is 'ORION'.
(Other definitions for orion that I've seen before include "Great hunter of Greek legend and a constellation" , "hero" , "Mythical Greek hunter turned into constellation" , "Constellation - mythological hunter" , "Constellation named for great Greek hunter" .)