What's in Paris? Eiffel Tower (4)
I believe the answer is:
rise
'tower' is the definition.
(I've seen this before)
'what's in paris? eiffel' is the wordplay.
'what's in' indicates the answer is hidden within the clue.
'RISE' is hidden in the letters of 'paris eiffel'.
(Other definitions for rise that I've seen before include "Tower" , "Soar" , "Move upwards" , "Hill" , "Ascend" .)