Nut aches badly having fallen (8)
I believe the answer is:
unchaste
'fallen' is the definition.
(I've seen this before)
'nut aches badly' is the wordplay.
'badly' indicates an anagram.
'nut'+'aches'='nutaches'
'nutaches' is an anagram of 'UNCHASTE'.
'having' is the link.
(Other definitions for unchaste that I've seen before include "Enjoying sex" , "very naughty" , "fallen" , "Immoral, wanton" , "Sexually immodest" .)