The pain of bachelorhood (4)
I believe the answer is:
ache
'the pain' is the definition.
(ache is a kind of pain)
'of bachelorhood' is the wordplay.
'of' says the answer is hidden in the clue.
'ACHE' can be found hidden inside 'bachelorhood'.
(Other definitions for ache that I've seen before include "Hanker" , "Play up" , "Similar" , "strong feeling" , "Feel sore" .)