Old flame worked as model — with nothing on? (7)
I believe the answer is:
exposed
'model with nothing on?' is the definition.
I can't judge whether this definition defines the answer.
'old flame worked' is the wordplay.
'old flame' becomes 'ex' (an ex-partner).
'worked' becomes 'posed' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'ex'+'posed'='EXPOSED'
'as' acts as a link.
Can you help me to learn more?
(Other definitions for exposed that I've seen before include "Unprotected from the weather" , "Made public" , "Shown up" , "Without protection" , "Not covered" .)