Where there are boats, there's a woman (6)
I believe the answer is:
marina
'where there' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'boats there's a woman' is the wordplay.
'boats there' becomes 'mar' (I can't explain this - if you can you should give a lot more credence to this answer).
'a woman' becomes 'Ina'.
'mar'+'ina'='MARINA'
'are' acts as a link.
Can you help me to learn more?
(Other definitions for marina that I've seen before include "Yacht station" , "Docking place for pleasure craft" , "place to moor up?" , "Base for pleasure boats" , "boating facility" .)