Nurse carries first lady to find river (6)
I believe the answer is:
severn
'river' is the definition.
(I've seen this before)
'nurse carries first lady' is the wordplay.
'nurse' becomes 'rn' (RN is an example).
'carries' means one lot of letters go next to another (in a down clue, some letters go beneath others).
'first lady' becomes 'seve' (I can't justify this - if you can you should believe this answer much more).
'rn' put after 'seve' is 'SEVERN'.
'to find' is the link.
Can you help me to learn more?
(Other definitions for severn that I've seen before include "Flower" , "River veers N" , "British banker" , "GB's longest river" , "England's longest river" .)