Peer, seeing a type of gas (5)
I believe the answer is:
noble
This clue is a double definition.
'peer' is the first definition.
(I've seen this before)
'a type of gas' is the second definition.
(I've seen this in another clue)
'seeing' acts as a link.
(Other definitions for noble that I've seen before include "Illustrious - old money" , "Worthy" , "Having high moral character" , "Lord" , "Honourable ? aristocratic" .)