Pain of bachelorhood (4)
I believe the answer is:
ache
'pain' is the definition.
(ache is a kind of pain)
'of bachelorhood' is the wordplay.
'of' indicates a hidden word.
'ACHE' can be found hidden inside 'bachelorhood'.
(Other definitions for ache that I've seen before include "Take an aspirin for it" , "Cause pain" , "anguish" , "Throb - hurt" , "burn" .)