After a little time in a bed, had let up (6)
I believe the answer is:
abated
'let up' is the definition.
(I've seen this in another clue)
'after a little time in a bed' is the wordplay.
'after' says to put letters next to each other.
'little time' becomes 't' (abbreviation for time).
'in' indicates putting letters inside.
'a' next to 't' is 'at'.
'a'+'bed'='abed'
'at' put inside 'abed' is 'ABATED'.
'had' is the link.
(Other definitions for abated that I've seen before include "grew smaller" , "dropped off" , "Became more moderate" , "grew less" , "weakened" .)