Sex in dilapidated motel providing a recurring theme (9)
I believe the answer is:
leitmotif
'a recurring theme' is the definition.
(recurring idea or image in a creative work)
'sex in dilapidated motel providing' is the wordplay.
'sex' becomes 'it' (a common euphemism).
'in' is an insertion indicator.
'dilapidated' indicates an anagram.
'providing' becomes 'if' (eg 'providing it's sunny' means 'if it's sunny').
'motel' with letters rearranged gives 'lemot'.
'it' inserted within 'lemot' is 'leitmot'.
'leitmot'+'if'='LEITMOTIF'
(Other definitions for leitmotif that I've seen before include "it's a repetitive strain" , "Recurrent theme" , "A melodic phrase that accompanies the reappearance of a person on stage" , "Recurring theme in literary composition" , "Recurring musical theme" .)