Model after topless sex show (6)
I believe the answer is:
expose
'show' is the definition.
(exposing is a kind of showing)
'model after topless sex' is the wordplay.
'model' becomes 'pose' (synonyms).
'after' means one lot of letters go next to another.
'topless' means to remove the first letter.
'sex' with its initial letter removed is 'ex'.
'pose' after 'ex' is 'EXPOSE'.
(Other definitions for expose that I've seen before include "Lay open, reveal" , "Make visible or apparent" , "Revelation of something discreditable - remove cover" , "Uncover or unmask" , "brings out crime" .)