Rise, to allow hosts sleep at last (8)
I believe the answer is:
gradient
'rise' is the definition.
(I've seen this before)
'allow hosts sleep at last' is the wordplay.
'allow' becomes 'grant' (synonyms).
'hosts' means one lot of letters goes inside another (inserted letters are welcomed or hosted).
'sleep at last' becomes 'die' (I can't justify this - if you can you should give a lot more credence to this answer).
'grant' going around 'die' is 'GRADIENT'.
'to' is the link.
Can you help me to learn more?
(Other definitions for gradient that I've seen before include "Measure of slope" , "Treading (anag) - slope" , "Level of steepness" , "Degree of slope in a road" , "Third OT book" .)