It illuminates honorable man joining institute in America (6)
I believe the answer is:
sirius
'it illuminates honorable' is the definition.
The definition suggests a singular noun which matches the answer.
'man joining institute in america' is the wordplay.
'man' becomes 'sir' (sir is a kind of man).
'joining' means one lot of letters go next to another.
'institute' becomes 'i' (common abbreviation as in MIT).
'in america' becomes 'U.S.' ('U.S.' is part of 'america').
'sir'+'i'+'us'='SIRIUS'
Can you help me to learn more?
(Other definitions for sirius that I've seen before include "Bright star" , "The Dogstar" , "Prominent star" , "The Dog Star, brightest of the fixed stars" , "Brightest star in the sky" .)