What the good-looking model is doing, being in an advantageous position (7,6)
I believe the answer is:
sitting pretty
'being in an advantageous position' is the definition.
(I've seen this in another clue)
'what the good-looking' is the wordplay.
'what' becomes 'sitting' (I can't explain this - if you can you should give a lot more credence to this answer).
'the good looking' becomes 'pretty'.
'sitting'+'pretty'='SITTING PRETTY'
'model is doing' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for sitting pretty that I've seen before include "Well placed" , "Descriptions of attractive model" , "Enjoying an advantageous position" , "Enjoying a good position" , "In a good position (posing as a model?)" .)