Detest a bore endlessly detaining husband (5)
I believe the answer is:
abhor
'detest' is the definition.
(abhorring is a kind of detesting)
'a bore endlessly detaining husband' is the wordplay.
'endlessly' means to remove the last letter.
'detaining' means one lot of letters goes inside another.
'husband' becomes 'h'.
'bore' with its last letter removed is 'bor'.
'bor' going around 'h' is 'bhor'.
'a'+'bhor'='ABHOR'
(Other definitions for abhor that I've seen before include "Can't bear" , "Execrate" , "Find horrible" , "Dislike very much" , "Regard with disgust and hatred" .)