Extreme comfort for those who have retired (8)
I believe the answer is:
bedsocks
'extreme comfort for those' is the definition.
I know nothing about this answer so I cannot tell whether this works.
'have retired' is the wordplay.
'have' becomes 'bed' (synonyms).
'retired' becomes 'socks' (I can't explain this - if you can you should give a lot more credence to this answer).
'bed'+'socks'='BEDSOCKS'
'who' is the link.
Can you help me to learn more?
(Other definitions for bedsocks that I've seen before include "Night-time footwear" , "Night wear for feet" , "Night attire" , "Night-time wear" , "Garments worn when asleep" .)